Interpretation of Prevalence Odds Ratio/Odds Ratio:
Interpretation of Prevalence Ratio/Risk Ratio:
References: Alexander, 2015a, Cummings, 2013, Tenny &Hoffman, 2019.
** https://www.medcalc.org/calc/odds_ratio.php (web-based confidence interval calculator of odds ratio)
*** https://www.medcalc.org/calc/relative_risk.php (web-based confidence interval calculator RR
In continuing with the obesity and sedentary activity level among HIV participants, the example below (see Table 1 ) describes the methods for calculating and discussing the results for an analytic cross-sectional study. The prevalence odds ratio (POR) (calculated as [ ad/bc] ) and prevalence ratio (PR) (calculated as [a/(a + b)]/ [c/(c + d)]) are commonly used to report estimates of association between independent and dependent variables in cross-sectional studies ( Tamhane, Westfall, Burkholder, & Cutter, 2016 ).
The POR is calculated similarly to the odds ratio (OR) ( Alexander, 2015b ) and referred to as POR when prevalence is used ( Tamhane et al., 2016 ). OR measures the association between exposure and outcome (see Table 1 ) and denotes the chances that an outcome happens with a specific exposure, compared to the chances of an outcome happening in the absence of the exposure (Szumilas, 2010). This information helps both clinicians and investigators determine if certain factors (i.e., clinical characteristics, medical history) are a risk for a particular outcome (i.e., disease, condition). Future studies or health policies can target methods to prevent or treat outcomes (i.e., disease, condition) identified in such studies.
For example, in Table 1 , using the formula and dataset below, the OR was 2.4. The result shows that the obese HIV participants (exposed) were two and a half times (2.5x) more likely to be sedentary than the non-obese participants (unexposed). If the OR for the dataset was equal to 1, then the exposure (obese) did not affect the outcome’s odds. In other words, the chance of being sedentary is the same in the exposed (obese) and the non-exposed (not obese) groups. Similarly, if the OR was less than 1, it implies that the exposed (obese) group, were less likely to be sedentary (outcome) compared to the non-obese group (unexposed) ( Tenny & Hoffman, 2019 ).
The PR is calculated similarly to the risk ratio (RR)( Alexander, 2015b ). The PR measures the prevalence of an outcome in the exposed group, divided by the unexposed group, and measures the association’s strength between the exposure and outcome (Alexander, 2015). Excess prevalence (EP) or the risk difference (RD) provides the difference in prevalence between the groups and indicates how much additional prevalence is due to the exposure of interest ( Alexander, 2015b ). From Table 1 , the PR/RR for the example equaled 2.07, with an EP of 11.9%. The results might conclude that obesity among the HIV participants was twice (2.07) as common and occurred almost 12% more often among HIV participants who were sedentary.
Similar to the OR interpretation, if the RR was equal to 1, exposure did not prevent or harm the exposed and unexposed groups. In other words, being obese did not affect the activity level (sedentary versus not sedentary). If the RR was less than 1, it implies that the exposure had a protective effect in that obese HIV participants were less likely to be sedentary than the unexposed group (not obese).
The statistical literature has numerous articles discussing the pros and cons of using either the POR/OR or PR/RR for cross-sectional studies ( Tamhane et al., 2016 ). Consulting a statistician to discuss the best choice for each project is highly recommended. However, according to Alexander and colleagues (2015a) , the POR is preferred when the study topic is a chronic condition (i.e., hypertension, HIV), or the risk of developing the disease takes several months to develop. For studies evaluating acute conditions (i.e., the common cold), the PR is favored ( Alexander, 2015a ).
Furthermore, suppose the prevalence of a disease or phenomena is low, less than ten percent in the exposed and unexposed population (sample). In that case, the resulting POR and PR will be equal ( Alexander, 2015a ). Since cross-sectional studies are suitable for examining chronic diseases or conditions, the POR is generally the ideal measure of association to use ( Alexander, 2015a ).
Confidence intervals (CI) measure the precision of the OR, RR, or the possible “variation in a point estimate (the mean value)” ( Alexander, 2015b , p 4). A narrower CI indicates a higher level of precision versus a wider CI suggesting a lower level of precision ( Cummings, 2013 ). The sample size also impacts the CI’s width, with larger sample sizes providing a more precise estimate. The approximate value of the point estimate is based on factors (i.e., characteristics like body weight, level of activity) such as the mean (average) of a population from a population’s random samples.
From Table 1 , the OR = 2.4 with a confidence interval of (95% CI (1.4713 – 3.9150)) might conclude that the obese HIV participants were two and a half times (2.5x) more likely to be sedentary than the non-obese participants. 2.4 is the point estimate obtained from this example; however, the entire population of obese HIV people was not included. If other samples of HIV participants were assessed, the point estimate would likely differ. Some samples might get the point estimate of less than or some greater than 2.4.
The 95% CI is the interval representing the (population) parameter value 95% of the time if an experiment or study is repeated, in that 95 out of 100 intervals would result in the intervals containing the true risk ratio or odds ratio value. For the sedentary and obesity study, the interpretation might conclude that a 2.4 point estimate could range from a low of 1.4713 to a high of 3.9150.
The main strength of the cross-sectional design is the ability to obtain results faster. Investigators do not need to wait for outcomes to occur. Participants either have the condition or attribute at the time of data collection or not. Furthermore, there are no participant follow-ups; therefore, losing study participants during the study is not an issue.
The design’s inherent nature makes it inexpensive to conduct and can yield multiple independent (predictor) and dependent (outcome) variables ( Cummings, 2013 ). The data collected can lead to additional studies to build upon the knowledge obtained. From the example, the investigators learned that obese HIV participants were more likely to be sedentary; the next study might develop a clinical trial to determine the methods to increase activity level in this population.
A significant limitation of using this design is the inability to measure the incidence of a disease or attribute ( Wang & Cheng, 2020 ). Incidence measures the proportion of participants that develop a disease or attribute over time ( Cummings, 2013 ). In other words, investigators need a follow-up phase to determine the incidence . In continuing with the example, if investigators continued to follow the HIV participants who were obese but not sedentary, would additional time (follow-up) result in increased sedentary behavior associated with conditions secondary to aging or worsening of immune status? Unfortunately, the cross-sectional design can not answer this question.
Additionally, the prevalence of a disease or attribute is influenced by the disease’s incidence and survival or disease duration ( Alexander, 2015a ). For example, participants who live longer with a disease will have a higher likelihood of being counted ( Prevalence = # of participants with the condition at the time point/ Total # of participants in the sample ) versus those who are short-term survivors. Moreover, if treatments for a disease or attribute are improved, or the survival time-frame decreases, the disease or attribute’s prevalence will reduce ( Alexander, 2015a ). New information presented to the lay public could also influence the prevalence of a disease or attribute through lifestyle changes (i.e., increasing physical activity, improving diet) or changing jobs if the profession is associated with an identified risk or disease. Therefore, this design does not allow investigators to ascertain the events’ sequence, which came first, obesity or sedentary behavior.
For investigators studying rare diseases or conditions, the cross-sectional design is not the best fit. Cross-sectional studies often draw samples from a large and heterogeneous study population ( Wang & Cheng, 2020 ). Participants with the rare condition of interest might not be identified in the study sample.
A reporting guideline for cross-sectional studies is available for investigators and consumers of research to use. A reporting guideline’s primary goal is to ensure that published clinical research studies provide transparency in reporting a study’s conduct (what was done) and results. The guideline is a tool investigators can use to develop their manuscripts and offers a checklist of inclusion items for a published paper (Equator.network). The recommended items will help ensure that a reader can understand the manuscript, follow the study’s planning and how the research was conducted, the findings, and the conclusions ( von Elm et al., 2014 ).
For cross-sectional studies, the guideline is titled Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) ( von Elm et al., 2014 ). The STROBE g uideline is a 22-item checklist. The checklist provides essential information for a study to be replicated, useful for healthcare professionals to make clinical decisions, and give enough information for inclusion in a systematic review ( https://www.equator-network.org/reporting-guidelines/strobe/ ).
The cross-sectional design is an appropriate method to determine the prevalence of a disease, attribute, or phenomena in a study sample. The design provides a ‘snapshot” of the sample, and investigators can describe their study sample and review associations between the collected variables (independent and dependent). The observational nature makes it relatively quick to complete a study and provides data to support future studies that might lead to methods to treat or prevent diseases or conditions.
This manuscript is supported in part by grant # UL1TR001866 from the National Center for Advancing Translational Sciences (NCATS), National Institutes of Health (NIH) Clinical and Translational Science Award (CTSA) program.
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A cross-sectional study is an experimental design that analyzes data from a representative sample at a specific point in time. Researchers usually evaluate multiple attributes at once when using this design. Unlike longitudinal studies , these studies don’t track changes over time.
Typically, researchers use this design to simply observe the prevalence of a condition or outcome at a specific moment and do not manipulate any variables or treatment conditions. This non-interference makes cross sectional studies a type of observational study . Think of it as taking a ‘photograph’ of a population at a particular time. Researchers collect data once, offering insights into various factors at that point.
Scientists use two broad types of cross-sectional studies:
While analysts can explore correlations between the variables in cross-sectional studies, these studies are not good at identifying causal relationships. Instead, they are relatively inexpensive and quick projects that can lay the groundwork for more in-depth longitudinal studies.
Imagine a study assessing the dietary habits of 5,000 people from different cities at one point in time. This study could reveal prevalent nutritional patterns and health indicators across these populations.
For example, researchers frequently use cross-sectional studies in the following fields:
Learn more about Experimental Designs: Definition and Types .
Cross-sectional studies are typically shorter in duration compared to longitudinal studies. They are conducted all at once, although the planning and analysis phases can span several months or a year.
When conducting a cross-sectional study, you face a critical decision: collect new data or use pre-existing datasets.
Many organizations, including governments and research institutes, frequently release data from cross-sectional studies. A classic example is the U.S. National Health and Nutrition Examination Survey (NHANES), which provides a snapshot of the nation’s health and nutritional status.
Such data is typically robust and can offer immediate insights. However, it’s less customizable than data you collect yourself. The data might be generalized to ensure privacy, limiting detailed analysis. Additionally, the original study’s variables restrict you, and you can’t modify data collection to meet your study’s needs.
If you choose pre-existing data, carefully evaluate the dataset’s source and the specifics of the data provided.
Opting to collect your own data gives you control over the variables and the nature of the information gathered. Here are some standard data collection methods for a cross-sectional study.
For all these methods, selecting a representative sample of your target population is crucial because it ensures the findings apply to the broader population and enhances the study’s overall validity and reliability .
Self-collected data can be tailored to your specific research question, offering depth and relevance. However, this approach requires carefully planning your sampling method to ensure representativeness and avoid biases.
In summary, whether you choose to use existing datasets or collect your own data, each approach has its own set of advantages and challenges. The key is aligning your choice with your research objectives and available resources.
A cross-sectional study can be efficient regarding time and resources, making it ideal for initial explorations that might not be possible with longitudinal studies.
These studies can also gather a vast amount of data on various variables at once from a large sample, allowing you to compare subgroups, all of which are more costly in longitudinal studies.
For example, imagine a cross-sectional study surveying 10,000 people nationwide about their dietary habits. This study can simultaneously collect data on numerous variables like age, income, education, and health status.
With such a comprehensive dataset, researchers can assess dietary patterns across different subgroups, such as comparing eating habits between urban and rural residents or analyzing how dietary choices vary with income levels. This ability to gather and compare many variables at once is a crucial strength of this research design, providing a rich, multifaceted snapshot of the population.
A cross-sectional study can identify correlations but not causal relationships . They record one-time measurements and can’t determine a sequence of events. In essence, they simultaneously measure possible causes and effects, making them hard to distinguish.
For example, a this type of research might find a correlation between high stress levels and poor sleep quality, but it can’t confirm if stress causes poor sleep or vice versa.
These studies provide only a snapshot and cannot track behaviors or trends over time. Consequently, they can’t establish how variables evolve or interact longitudinally.
For example, a survey conducted during an economic downturn might reflect unusually high levels of financial stress in the population, which may not be indicative of general long-term trends.
In conclusion, cross-sectional studies offer valuable insights into the status of a population at a specific point. They are handy for exploratory research and identifying potential areas for more in-depth study. Understanding their strengths and limitations is crucial for researchers to utilize this method effectively.
Wang, X., & Cheng, Z. (2020). Cross-Sectional Studies: Strengths, Weaknesses, and Recommendations . Chest, 158(1), S65-S71. DOI:10.1016/j.chest.2020.03.012.
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Quantitative study designs.
Cross-Sectional Study
The Australian Census run by the Australian Bureau of Statistics, is an example of a whole of population cross-sectional study.
Data on a number of aspects of the Australian population is gathered through completion of a survey within every Australian household on the same night. This provides a snapshot of the Australian population at that instance.
Cross-sectional studies look at a population at a single point in time, like taking a slice or cross-section of a group, and variables are recorded for each participant.
This may be a single snapshot for one point in time or may look at a situation at one point in time and then follow it up with another or multiple snapshots at later points; this is then termed a repeated cross-sectional data analysis.
Repeated Cross-Sectional Data Analysis
Please note the Introduction , where there is a table under "Which study type will answer my clinical question?" . You may find that there are only one or two question types that your study answers – that’s ok.
Cross-sectional study designs are useful when:
Frequency | How common is the outcome (disease, risk factor, etc.)? | This is of the common mental disorders among Indigenous people living in regional, remote and metropolitan Australia. |
---|---|---|
Aetiology | What risk factors are associated with these outcomes? | This identifies the characteristics of women calling the perinatal anxiety & depression Australia (PANDA) national helpline. |
Diagnosis | Does the new test perform as well as the ‘gold standard’? | This investigates the accuracy of a Client Satisfaction Questionnaire in relation to client satisfaction in mental health service support. |
Cross-sectional studies are at risk of participation bias, or low response rates from participants. If a large number of surveys are sent out and only a quarter are completed and returned then this becomes an issue as those who responded may not be a true representation of the overall population.
To assist with critically appraising cross-sectional studies there are some tools / checklists you can use.
The Australian National Survey of Mental Health and Wellbeing (NSMHWB)
https://www.abs.gov.au/statistics/health/mental-health/national-survey-mental-health-and-wellbeing-summary-results/2007
A widely known example of cross-sectional study design, the Australian National Survey of Mental Health and Wellbeing (NSMHWB). This study was a national epidemiological survey of mental disorders investigating the questions: How many people meet DSM-IV and ICD-10 diagnostic criteria for the major mental disorders? How disabled are they by their mental disorders? And, how many have seen a health professional for their mental disorder?
Australian Government Department of Health. (2003). The Australian National Survey of Mental Health and Wellbeing (NSMHWB). 2019, from https://www.abs.gov.au/statistics/health/mental-health/national-survey-mental-health-and-wellbeing-summary-results/2007
Bowers, D. a., Bewick, B., House, A., & Owens, D. (2013). Understanding clinical papers (Third edition. ed.): Wiley Blackwell.
Gravetter, F. J. a., & Forzano, L.-A. B. (2012). Research methods for the behavioral sciences (Fourth edition. ed.): Wadsworth Cengage Learning.
Greenhalgh, T. a. (2014). How to read a paper : the basics of evidence-based medicine (Fifth edition. ed.): John Wiley & Sons Inc.
Hoffmann, T. a., Bennett, S. P., & Mar, C. D. (2017). Evidence-Based Practice Across the Health Professions (Third edition. ed.): Elsevier.
Howitt, D., & Cramer, D. (2008). Introduction to research methods in psychology (Second edition. ed.): Prentice Hall.
Kelly, P. J., Kyngdon, F., Ingram, I., Deane, F. P., Baker, A. L., & Osborne, B. A. (2018). The Client Satisfaction Questionnaire‐8: Psychometric properties in a cross‐sectional survey of people attending residential substance abuse treatment. Drug and Alcohol Review, 37(1), 79-86. doi: 10.1111/dar.12522
Lawrence, D., Hancock, K. J., & Kisely, S. (2013). The gap in life expectancy from preventable physical illness in psychiatric patients in Western Australia: retrospective analysis of population based registers. BMJ: British Medical Journal, 346(7909), 13-13.
Nasir, B. F., Toombs, M. R., Kondalsamy-Chennakesavan, S., Kisely, S., Gill, N. S., Black, E., Ranmuthugala, G., Ostini, R., Nicholson, G. C., Hayman, N., & Beccaria, G.. (2018). Common mental disorders among Indigenous people living in regional, remote and metropolitan Australia: A cross-sectional study. BMJ Open , 8 (6). https://doi.org/10.1136/bmjopen-2017-020196
Robson, C., & McCartan, K. (2016). Real world research (Fourth Edition. ed.): Wiley.
Sedgwick, P. (2014). Cross sectional studies: advantages and disadvantages. BMJ : British Medical Journal, 348, g2276. doi: 10.1136/bmj.g2276
Setia, M. S. (2016). Methodology Series Module 3: Cross-sectional Studies. Indian journal of dermatology, 61(3), 261-264. doi: 10.4103/0019-5154.182410
Shafiei, T., Biggs, L. J., Small, R., McLachlan, H. L., & Forster, D. A. (2018). Characteristics of women calling the panda perinatal anxiety & depression australia national helpline: A cross-sectional study. Archives of Women's Mental Health. doi: 10.1007/s00737-018-0868-4
Van Heyningen, T., Honikman, S., Myer, L., Onah, M. N., Field, S., & Tomlinson, M. (2017). Prevalence and predictors of anxiety disorders amongst low-income pregnant women in urban South Africa: a cross-sectional study. Archives of Women's Mental Health(6), 765. doi: 10.1007/s00737-017-0768-z
Vogt, W. P. (2005). Dictionary of statistics & methodology : a nontechnical guide for the social sciences (Third edition. ed.): Sage Publications.
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A cross-sectional study is used to collect data from a population simultaneously. It is a snapshot of the population at a particular moment rather than a study that tracks changes over time. This design is often used in fields such as public health, sociology, and psychology to gather information about the characteristics, attitudes, and behaviors of a group of individuals .
This blog will discuss what cross-sectional studies are. We’ll review examples and explain the types of cross-sectional studies you might perform. We’ll also take a closer look at the benefits of this valuable research for the work you do.
A cross-sectional study is a type of observational research that analyzes data of variables collected at one given point in time across a sample population or a pre-defined subset.
This study type is also known as cross-sectional analysis, transverse study, or prevalence study. Although this research does not involve conducting experiments, researchers often use it to understand outcomes in the physical and social sciences and many business industries.
When researchers conduct cross-sectional studies, they look at a specific group of people at a single point in time. Here are some simple characteristics of cross-sectional studies that might help you understand them better:
Want a fitting metaphor? Think of a snapshot of a group of people at one event, say a family reunion. The people in that extended family are used to determine what is happening in real-time at the moment.
All people have at least one variable in common – being related – and multiple variables they do not share. You could make all kinds of observations and analyses from that starting point. Hence, this research type “takes the pulse” of population data at any given time.
You can also use this type of research to map prevailing variables that exist at a particular given point—for example, cross-sectional data on past drinking habits and a current diagnosis of liver failure.
The data collected in cross-sectional studies involves subjects or participants who are similar in all variables – except the one that is under review. This variable remains constant throughout the study. This is unlike a longitudinal study , where variables can change throughout the research. Consider these examples for more clarity:
This research allows scholars and strategists to quickly collect cross-sectional data that helps in decision-making and offering products or services.
When you conduct a cross-sectional research study, you will engage in one or both types of research: descriptive or analytical. Read their descriptions to see how they might apply to your work.
Researchers usually use descriptive and analytical research methods in real-life cross-sectional studies.
Are you curious whether this research is the right approach for your next study? A Cross-Sectional Survey is an efficient and revealing way to collect data. Check out some of the critical advantages of conducting online research using cross-sectional studies and see if it’s a good fit for your needs.
If you are looking for an approach that studies subjects and variables over time, you might prefer a longitudinal study. Additionally, you could follow your research with a longitudinal study. It is easy to confuse the two research methods, so we’ve broken it down here:
We recently published a blog that talks about Causal Research ; why don’t you check it out for more ideas?
Although they are both quantitative research methods, there are a few differences when comparing and contrasting cross-sectional and longitudinal studies .
Criteria | Cross-Sectional Study | Longitudinal Study |
---|---|---|
Data Collection | Collect data at one point in time. | Collect data at multiple time points. |
Analysis | Data was analyzed based on within-subject changes. | A shorter time is required. |
Participants | Different individuals at each point in time. | Same individuals over time. |
Time | A shorter time is required. | Longer time required. |
Strengths | Quick and cost-effective. | Tracks individual changes over time. |
Bias | It may have more bias due to cohort effects. | It may have less bias due to cohort effects. |
Limitations | Cannot determine causality | Time-consuming and costly |
Example | A survey of different age groups’ attitudes toward social media. | A study tracking changes in individuals’ attitudes towards social media over time. |
Researchers prefer cross-sectional studies to find common points between variables. Still, they use longitudinal studies, due to their nature, to dissect the research from the cross-sectional studies for further research.
Now that you have a better understanding of what cross-sectional research is and how to perform your studies, let’s look at two examples in more detail:
Phone companies rely on advanced and innovative features to drive sales. Research by a phone manufacturer throughout the target demographic market validates the expected adoption rate and potential phone sales. In cross-sectional studies, researchers enroll men and women across regions and age ranges for research.
If the results show that Asian women would not buy the phone because it is bulky, the mobile phone company can tweak the design to make it less bulky. They can also develop and market a smaller phone to appeal to a more inclusive group of women.
Another example of a cross-sectional study would be a medical study examining the prevalence of cancer amongst a defined population. The researcher can evaluate people of different ages, ethnicities, geographical locations, and social backgrounds.
If a significant number of men from a particular age group are more prone to have the disease, the researcher can conduct further studies to understand the reasons. A longitudinal study is best used, in this case, to study the same participants over time.
It’s your turn! Whether you’re building a marketing strategy or performing a cutting-edge medical study, you can get started by creating an intuitive survey from QuestionPro. Please choose from one of our 350+ survey templates, or build your own and leverage our reporting tools to discover deep insights to apply to your best work.
You can use single-ease questions . A single-ease research question is a straightforward query that elicits a concise and uncomplicated response.
Also, you can find advanced data analysis tools such as trend analysis and dashboards to visualize your information and do your own cross-sectional studies simply and efficiently.
A cross-sectional study provides valuable insights into a population’s characteristics, attitudes, and behaviors at a single point in time. As with any research design , cross-sectional studies should be used with other research methods to provide a complete study. Overall, cross-sectional studies can be a valuable tool for researchers looking to understand a population quickly.
With QuestionPro, you can conduct cross-sectional studies with ease. QuestionPro provides various tools for analyzing your collected data, cross-tabulation, and more. Whether you’re a researcher, marketer, or business professional, QuestionPro can help you gather the data you need to make informed decisions.
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A cross-sectional study is a type of research that collects data from a group of people at a single point in time to analyze characteristics and relationships.
They are valuable for understanding the current status of a condition or behavior within a population, making them great for initial assessments.
Cross-sectional studies capture data at a one-time point, while longitudinal studies track the same individuals over an extended period to observe changes.
It’s cost-effective, quick to conduct, and provides a broad view of a population’s characteristics or behaviors at a specific time.
The primary goal of a cross-sectional study is to examine and analyze the relationships or associations between different variables within a population at a specific point in time.
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A cross-sectional study is a research methodology that involves collecting data on a sample of individuals at one specific point in time.
The researcher(s) will collect data on various factors, all at the one time, and observe how those variables are related to other factors.
In this type of study, researchers do not manipulate any variables, but rather observe their interconnected influence on specific variables within the sample of individuals being studied.
The usual purpose of cross-sectional research is descriptive; to paint a picture of an existing relation between variables within a given population or subgroup.
Cross-sectional studies are often implemented in developmental psychology to examine factors that impact children, medical research to identify determinants of certain health outcomes, or in economics research to understand how predictor variables relate to outcome variables.
In a cross-sectional study, the sample of individuals studied is extremely important. Sample groups can be one of two types: heterogeneous or homogeneous .
The more homogeneous the sample, the less generalizability the study’s results have to the wider population.
For example, a sample of college students may allow comparisons within males and females in that sample, but it will be difficult to say the results apply to older populations or non-college students.
Cross-sectional research collects data on one sample at one point in time, whereas longitudinal research collects multiple datapoints over a longer period of time.
A cross-sectional study allows researchers to make comparisons among different groups within the sample, but is not particularly useful for analyzing changes over time.
Longitudinal research collects data on the same sample over a longer period of time.
Sometimes that period of time will consist of just a few years, while in other studies it could consist of decades, depending on the study’s purpose. Collecting data over a several years or decades allows researchers to examine how variables change over time.
An important difference between the two types of research has to do with the concept of causality .
Ideally, researchers want to know what causes behavior or a health outcome.
Many types of research designs do not allow the assessment of causality. Researchers can identify factors that are related to , or connected with , or even statistically correlated with , other variables, but each of those terms is weaker than the notion of causality.
Because longitudinal research occurs over time, researchers have more confidence on inferring causality among predictor variables and outcome variables.
Note however, that because longitudinal research does not involve the researchers manipulating the level of a variable, inferences regarding causality are still cautionary.
Cross-sectional research involves only static data collected at a single point in time. Therefore, inferences regarding causality cannot be made.
Advantages | Disadvantages |
---|---|
Utilizes existing databases for efficient and inexpensive data collection. | It’s impossible to determine causality due to observational nature and single-point data collection. |
Helps related to certain outcomes in fields like medicine or psychology. | Relies on self-reported data, which may not always be accurate due to factors like social desirability bias or . |
Allows comparison of different segments within a large sample. | There may be issues with sample’s characteristics, such as lack of heterogeneity or small size. |
Offers large datasets with numerous variables that can be analyzed for insights using advanced statistical procedures. | There can be poor response rates, limiting the dataset and potentially affecting the results of the study. |
Cross-sectional studies that are representative of larger populations can establish plausible generalizability, unlike . | While a longitudinal study can establish clear correlations (e.g. “the men in the cohort had higher income than the women in the cohort”), they cannot explain what caused those correlations. |
For a full discussion of the strengths and weaknesses of cross-sectional research, see my article here .
A cross-sectional study is a valuable research methodology that allows scientists to determine the relationship between different variables and how they are connected with a specific outcome variable.
The procedure involves collecting data from one group of individuals at the same time. This can be accomplished by distributing surveys or by accessing large data sets that are maintained by government institutions or private companies.
The advantages of cross-sectional research include the ease and efficiency of collecting lots of data, the opportunity to examine how numerous factors are related, and the ability to identify factors that should be studied further.
One of the biggest disadvantages of cross-sectional research is not being able to infer a causal relationship between the factors studied and the outcome variable of primary interest.
Other disadvantages include low response rates, participants unable or unwilling to answer questions accurately and honestly, or the characteristic of the sample limiting the generalizability of the results.
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Cross-sectional studies are observational studies that analyze data from a population at a single point in time. They are often used to measure the prevalence of health outcomes, understand determinants of health, and describe features of a population. Unlike other types of observational studies, cross-sectional studies do not follow individuals up over time. They are usually inexpensive and easy to conduct. They are useful for establishing preliminary evidence in planning a future advanced study. This article reviews the essential characteristics, describes strengths and weaknesses, discusses methodological issues, and gives our recommendations on design and statistical analysis for cross-sectional studies in pulmonary and critical care medicine. A list of considerations for reviewers is also provided.
Keywords: bias; confounding; cross-sectional studies; prevalence; sampling.
Copyright © 2020 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.
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What is the difference between a longitudinal study and a cross-sectional study.
Longitudinal studies and cross-sectional studies are two different types of research design . In a cross-sectional study you collect data from a population at a specific point in time; in a longitudinal study you repeatedly collect data from the same sample over an extended period of time.
Longitudinal study | Cross-sectional study |
---|---|
observations | Observations at a in time |
Observes the multiple times | Observes (a “cross-section”) in the population |
Follows in participants over time | Provides of society at a given point |
Attrition refers to participants leaving a study. It always happens to some extent—for example, in randomized controlled trials for medical research.
Differential attrition occurs when attrition or dropout rates differ systematically between the intervention and the control group . As a result, the characteristics of the participants who drop out differ from the characteristics of those who stay in the study. Because of this, study results may be biased .
Action research is conducted in order to solve a particular issue immediately, while case studies are often conducted over a longer period of time and focus more on observing and analyzing a particular ongoing phenomenon.
Action research is focused on solving a problem or informing individual and community-based knowledge in a way that impacts teaching, learning, and other related processes. It is less focused on contributing theoretical input, instead producing actionable input.
Action research is particularly popular with educators as a form of systematic inquiry because it prioritizes reflection and bridges the gap between theory and practice. Educators are able to simultaneously investigate an issue as they solve it, and the method is very iterative and flexible.
A cycle of inquiry is another name for action research . It is usually visualized in a spiral shape following a series of steps, such as “planning → acting → observing → reflecting.”
To make quantitative observations , you need to use instruments that are capable of measuring the quantity you want to observe. For example, you might use a ruler to measure the length of an object or a thermometer to measure its temperature.
Criterion validity and construct validity are both types of measurement validity . In other words, they both show you how accurately a method measures something.
While construct validity is the degree to which a test or other measurement method measures what it claims to measure, criterion validity is the degree to which a test can predictively (in the future) or concurrently (in the present) measure something.
Construct validity is often considered the overarching type of measurement validity . You need to have face validity , content validity , and criterion validity in order to achieve construct validity.
Convergent validity and discriminant validity are both subtypes of construct validity . Together, they help you evaluate whether a test measures the concept it was designed to measure.
You need to assess both in order to demonstrate construct validity. Neither one alone is sufficient for establishing construct validity.
Content validity shows you how accurately a test or other measurement method taps into the various aspects of the specific construct you are researching.
In other words, it helps you answer the question: “does the test measure all aspects of the construct I want to measure?” If it does, then the test has high content validity.
The higher the content validity, the more accurate the measurement of the construct.
If the test fails to include parts of the construct, or irrelevant parts are included, the validity of the instrument is threatened, which brings your results into question.
Face validity and content validity are similar in that they both evaluate how suitable the content of a test is. The difference is that face validity is subjective, and assesses content at surface level.
When a test has strong face validity, anyone would agree that the test’s questions appear to measure what they are intended to measure.
For example, looking at a 4th grade math test consisting of problems in which students have to add and multiply, most people would agree that it has strong face validity (i.e., it looks like a math test).
On the other hand, content validity evaluates how well a test represents all the aspects of a topic. Assessing content validity is more systematic and relies on expert evaluation. of each question, analyzing whether each one covers the aspects that the test was designed to cover.
A 4th grade math test would have high content validity if it covered all the skills taught in that grade. Experts(in this case, math teachers), would have to evaluate the content validity by comparing the test to the learning objectives.
Snowball sampling is a non-probability sampling method . Unlike probability sampling (which involves some form of random selection ), the initial individuals selected to be studied are the ones who recruit new participants.
Because not every member of the target population has an equal chance of being recruited into the sample, selection in snowball sampling is non-random.
Snowball sampling is a non-probability sampling method , where there is not an equal chance for every member of the population to be included in the sample .
This means that you cannot use inferential statistics and make generalizations —often the goal of quantitative research . As such, a snowball sample is not representative of the target population and is usually a better fit for qualitative research .
Snowball sampling relies on the use of referrals. Here, the researcher recruits one or more initial participants, who then recruit the next ones.
Participants share similar characteristics and/or know each other. Because of this, not every member of the population has an equal chance of being included in the sample, giving rise to sampling bias .
Snowball sampling is best used in the following cases:
The reproducibility and replicability of a study can be ensured by writing a transparent, detailed method section and using clear, unambiguous language.
Reproducibility and replicability are related terms.
Stratified sampling and quota sampling both involve dividing the population into subgroups and selecting units from each subgroup. The purpose in both cases is to select a representative sample and/or to allow comparisons between subgroups.
The main difference is that in stratified sampling, you draw a random sample from each subgroup ( probability sampling ). In quota sampling you select a predetermined number or proportion of units, in a non-random manner ( non-probability sampling ).
Purposive and convenience sampling are both sampling methods that are typically used in qualitative data collection.
A convenience sample is drawn from a source that is conveniently accessible to the researcher. Convenience sampling does not distinguish characteristics among the participants. On the other hand, purposive sampling focuses on selecting participants possessing characteristics associated with the research study.
The findings of studies based on either convenience or purposive sampling can only be generalized to the (sub)population from which the sample is drawn, and not to the entire population.
Random sampling or probability sampling is based on random selection. This means that each unit has an equal chance (i.e., equal probability) of being included in the sample.
On the other hand, convenience sampling involves stopping people at random, which means that not everyone has an equal chance of being selected depending on the place, time, or day you are collecting your data.
Convenience sampling and quota sampling are both non-probability sampling methods. They both use non-random criteria like availability, geographical proximity, or expert knowledge to recruit study participants.
However, in convenience sampling, you continue to sample units or cases until you reach the required sample size.
In quota sampling, you first need to divide your population of interest into subgroups (strata) and estimate their proportions (quota) in the population. Then you can start your data collection, using convenience sampling to recruit participants, until the proportions in each subgroup coincide with the estimated proportions in the population.
A sampling frame is a list of every member in the entire population . It is important that the sampling frame is as complete as possible, so that your sample accurately reflects your population.
Stratified and cluster sampling may look similar, but bear in mind that groups created in cluster sampling are heterogeneous , so the individual characteristics in the cluster vary. In contrast, groups created in stratified sampling are homogeneous , as units share characteristics.
Relatedly, in cluster sampling you randomly select entire groups and include all units of each group in your sample. However, in stratified sampling, you select some units of all groups and include them in your sample. In this way, both methods can ensure that your sample is representative of the target population .
A systematic review is secondary research because it uses existing research. You don’t collect new data yourself.
The key difference between observational studies and experimental designs is that a well-done observational study does not influence the responses of participants, while experiments do have some sort of treatment condition applied to at least some participants by random assignment .
An observational study is a great choice for you if your research question is based purely on observations. If there are ethical, logistical, or practical concerns that prevent you from conducting a traditional experiment , an observational study may be a good choice. In an observational study, there is no interference or manipulation of the research subjects, as well as no control or treatment groups .
It’s often best to ask a variety of people to review your measurements. You can ask experts, such as other researchers, or laypeople, such as potential participants, to judge the face validity of tests.
While experts have a deep understanding of research methods , the people you’re studying can provide you with valuable insights you may have missed otherwise.
Face validity is important because it’s a simple first step to measuring the overall validity of a test or technique. It’s a relatively intuitive, quick, and easy way to start checking whether a new measure seems useful at first glance.
Good face validity means that anyone who reviews your measure says that it seems to be measuring what it’s supposed to. With poor face validity, someone reviewing your measure may be left confused about what you’re measuring and why you’re using this method.
Face validity is about whether a test appears to measure what it’s supposed to measure. This type of validity is concerned with whether a measure seems relevant and appropriate for what it’s assessing only on the surface.
Statistical analyses are often applied to test validity with data from your measures. You test convergent validity and discriminant validity with correlations to see if results from your test are positively or negatively related to those of other established tests.
You can also use regression analyses to assess whether your measure is actually predictive of outcomes that you expect it to predict theoretically. A regression analysis that supports your expectations strengthens your claim of construct validity .
When designing or evaluating a measure, construct validity helps you ensure you’re actually measuring the construct you’re interested in. If you don’t have construct validity, you may inadvertently measure unrelated or distinct constructs and lose precision in your research.
Construct validity is often considered the overarching type of measurement validity , because it covers all of the other types. You need to have face validity , content validity , and criterion validity to achieve construct validity.
Construct validity is about how well a test measures the concept it was designed to evaluate. It’s one of four types of measurement validity , which includes construct validity, face validity , and criterion validity.
There are two subtypes of construct validity.
Naturalistic observation is a valuable tool because of its flexibility, external validity , and suitability for topics that can’t be studied in a lab setting.
The downsides of naturalistic observation include its lack of scientific control , ethical considerations , and potential for bias from observers and subjects.
Naturalistic observation is a qualitative research method where you record the behaviors of your research subjects in real world settings. You avoid interfering or influencing anything in a naturalistic observation.
You can think of naturalistic observation as “people watching” with a purpose.
A dependent variable is what changes as a result of the independent variable manipulation in experiments . It’s what you’re interested in measuring, and it “depends” on your independent variable.
In statistics, dependent variables are also called:
An independent variable is the variable you manipulate, control, or vary in an experimental study to explore its effects. It’s called “independent” because it’s not influenced by any other variables in the study.
Independent variables are also called:
As a rule of thumb, questions related to thoughts, beliefs, and feelings work well in focus groups. Take your time formulating strong questions, paying special attention to phrasing. Be careful to avoid leading questions , which can bias your responses.
Overall, your focus group questions should be:
A structured interview is a data collection method that relies on asking questions in a set order to collect data on a topic. They are often quantitative in nature. Structured interviews are best used when:
More flexible interview options include semi-structured interviews , unstructured interviews , and focus groups .
Social desirability bias is the tendency for interview participants to give responses that will be viewed favorably by the interviewer or other participants. It occurs in all types of interviews and surveys , but is most common in semi-structured interviews , unstructured interviews , and focus groups .
Social desirability bias can be mitigated by ensuring participants feel at ease and comfortable sharing their views. Make sure to pay attention to your own body language and any physical or verbal cues, such as nodding or widening your eyes.
This type of bias can also occur in observations if the participants know they’re being observed. They might alter their behavior accordingly.
The interviewer effect is a type of bias that emerges when a characteristic of an interviewer (race, age, gender identity, etc.) influences the responses given by the interviewee.
There is a risk of an interviewer effect in all types of interviews , but it can be mitigated by writing really high-quality interview questions.
A semi-structured interview is a blend of structured and unstructured types of interviews. Semi-structured interviews are best used when:
An unstructured interview is the most flexible type of interview, but it is not always the best fit for your research topic.
Unstructured interviews are best used when:
The four most common types of interviews are:
Deductive reasoning is commonly used in scientific research, and it’s especially associated with quantitative research .
In research, you might have come across something called the hypothetico-deductive method . It’s the scientific method of testing hypotheses to check whether your predictions are substantiated by real-world data.
Deductive reasoning is a logical approach where you progress from general ideas to specific conclusions. It’s often contrasted with inductive reasoning , where you start with specific observations and form general conclusions.
Deductive reasoning is also called deductive logic.
There are many different types of inductive reasoning that people use formally or informally.
Here are a few common types:
Inductive reasoning is a bottom-up approach, while deductive reasoning is top-down.
Inductive reasoning takes you from the specific to the general, while in deductive reasoning, you make inferences by going from general premises to specific conclusions.
In inductive research , you start by making observations or gathering data. Then, you take a broad scan of your data and search for patterns. Finally, you make general conclusions that you might incorporate into theories.
Inductive reasoning is a method of drawing conclusions by going from the specific to the general. It’s usually contrasted with deductive reasoning, where you proceed from general information to specific conclusions.
Inductive reasoning is also called inductive logic or bottom-up reasoning.
A hypothesis states your predictions about what your research will find. It is a tentative answer to your research question that has not yet been tested. For some research projects, you might have to write several hypotheses that address different aspects of your research question.
A hypothesis is not just a guess — it should be based on existing theories and knowledge. It also has to be testable, which means you can support or refute it through scientific research methods (such as experiments, observations and statistical analysis of data).
Triangulation can help:
But triangulation can also pose problems:
There are four main types of triangulation :
Many academic fields use peer review , largely to determine whether a manuscript is suitable for publication. Peer review enhances the credibility of the published manuscript.
However, peer review is also common in non-academic settings. The United Nations, the European Union, and many individual nations use peer review to evaluate grant applications. It is also widely used in medical and health-related fields as a teaching or quality-of-care measure.
Peer assessment is often used in the classroom as a pedagogical tool. Both receiving feedback and providing it are thought to enhance the learning process, helping students think critically and collaboratively.
Peer review can stop obviously problematic, falsified, or otherwise untrustworthy research from being published. It also represents an excellent opportunity to get feedback from renowned experts in your field. It acts as a first defense, helping you ensure your argument is clear and that there are no gaps, vague terms, or unanswered questions for readers who weren’t involved in the research process.
Peer-reviewed articles are considered a highly credible source due to this stringent process they go through before publication.
In general, the peer review process follows the following steps:
Exploratory research is often used when the issue you’re studying is new or when the data collection process is challenging for some reason.
You can use exploratory research if you have a general idea or a specific question that you want to study but there is no preexisting knowledge or paradigm with which to study it.
Exploratory research is a methodology approach that explores research questions that have not previously been studied in depth. It is often used when the issue you’re studying is new, or the data collection process is challenging in some way.
Explanatory research is used to investigate how or why a phenomenon occurs. Therefore, this type of research is often one of the first stages in the research process , serving as a jumping-off point for future research.
Exploratory research aims to explore the main aspects of an under-researched problem, while explanatory research aims to explain the causes and consequences of a well-defined problem.
Explanatory research is a research method used to investigate how or why something occurs when only a small amount of information is available pertaining to that topic. It can help you increase your understanding of a given topic.
Clean data are valid, accurate, complete, consistent, unique, and uniform. Dirty data include inconsistencies and errors.
Dirty data can come from any part of the research process, including poor research design , inappropriate measurement materials, or flawed data entry.
Data cleaning takes place between data collection and data analyses. But you can use some methods even before collecting data.
For clean data, you should start by designing measures that collect valid data. Data validation at the time of data entry or collection helps you minimize the amount of data cleaning you’ll need to do.
After data collection, you can use data standardization and data transformation to clean your data. You’ll also deal with any missing values, outliers, and duplicate values.
Every dataset requires different techniques to clean dirty data , but you need to address these issues in a systematic way. You focus on finding and resolving data points that don’t agree or fit with the rest of your dataset.
These data might be missing values, outliers, duplicate values, incorrectly formatted, or irrelevant. You’ll start with screening and diagnosing your data. Then, you’ll often standardize and accept or remove data to make your dataset consistent and valid.
Data cleaning is necessary for valid and appropriate analyses. Dirty data contain inconsistencies or errors , but cleaning your data helps you minimize or resolve these.
Without data cleaning, you could end up with a Type I or II error in your conclusion. These types of erroneous conclusions can be practically significant with important consequences, because they lead to misplaced investments or missed opportunities.
Data cleaning involves spotting and resolving potential data inconsistencies or errors to improve your data quality. An error is any value (e.g., recorded weight) that doesn’t reflect the true value (e.g., actual weight) of something that’s being measured.
In this process, you review, analyze, detect, modify, or remove “dirty” data to make your dataset “clean.” Data cleaning is also called data cleansing or data scrubbing.
Research misconduct means making up or falsifying data, manipulating data analyses, or misrepresenting results in research reports. It’s a form of academic fraud.
These actions are committed intentionally and can have serious consequences; research misconduct is not a simple mistake or a point of disagreement but a serious ethical failure.
Anonymity means you don’t know who the participants are, while confidentiality means you know who they are but remove identifying information from your research report. Both are important ethical considerations .
You can only guarantee anonymity by not collecting any personally identifying information—for example, names, phone numbers, email addresses, IP addresses, physical characteristics, photos, or videos.
You can keep data confidential by using aggregate information in your research report, so that you only refer to groups of participants rather than individuals.
Research ethics matter for scientific integrity, human rights and dignity, and collaboration between science and society. These principles make sure that participation in studies is voluntary, informed, and safe.
Ethical considerations in research are a set of principles that guide your research designs and practices. These principles include voluntary participation, informed consent, anonymity, confidentiality, potential for harm, and results communication.
Scientists and researchers must always adhere to a certain code of conduct when collecting data from others .
These considerations protect the rights of research participants, enhance research validity , and maintain scientific integrity.
In multistage sampling , you can use probability or non-probability sampling methods .
For a probability sample, you have to conduct probability sampling at every stage.
You can mix it up by using simple random sampling , systematic sampling , or stratified sampling to select units at different stages, depending on what is applicable and relevant to your study.
Multistage sampling can simplify data collection when you have large, geographically spread samples, and you can obtain a probability sample without a complete sampling frame.
But multistage sampling may not lead to a representative sample, and larger samples are needed for multistage samples to achieve the statistical properties of simple random samples .
These are four of the most common mixed methods designs :
Triangulation in research means using multiple datasets, methods, theories and/or investigators to address a research question. It’s a research strategy that can help you enhance the validity and credibility of your findings.
Triangulation is mainly used in qualitative research , but it’s also commonly applied in quantitative research . Mixed methods research always uses triangulation.
In multistage sampling , or multistage cluster sampling, you draw a sample from a population using smaller and smaller groups at each stage.
This method is often used to collect data from a large, geographically spread group of people in national surveys, for example. You take advantage of hierarchical groupings (e.g., from state to city to neighborhood) to create a sample that’s less expensive and time-consuming to collect data from.
No, the steepness or slope of the line isn’t related to the correlation coefficient value. The correlation coefficient only tells you how closely your data fit on a line, so two datasets with the same correlation coefficient can have very different slopes.
To find the slope of the line, you’ll need to perform a regression analysis .
Correlation coefficients always range between -1 and 1.
The sign of the coefficient tells you the direction of the relationship: a positive value means the variables change together in the same direction, while a negative value means they change together in opposite directions.
The absolute value of a number is equal to the number without its sign. The absolute value of a correlation coefficient tells you the magnitude of the correlation: the greater the absolute value, the stronger the correlation.
These are the assumptions your data must meet if you want to use Pearson’s r :
Quantitative research designs can be divided into two main categories:
Qualitative research designs tend to be more flexible. Common types of qualitative design include case study , ethnography , and grounded theory designs.
A well-planned research design helps ensure that your methods match your research aims, that you collect high-quality data, and that you use the right kind of analysis to answer your questions, utilizing credible sources . This allows you to draw valid , trustworthy conclusions.
The priorities of a research design can vary depending on the field, but you usually have to specify:
A research design is a strategy for answering your research question . It defines your overall approach and determines how you will collect and analyze data.
Questionnaires can be self-administered or researcher-administered.
Self-administered questionnaires can be delivered online or in paper-and-pen formats, in person or through mail. All questions are standardized so that all respondents receive the same questions with identical wording.
Researcher-administered questionnaires are interviews that take place by phone, in-person, or online between researchers and respondents. You can gain deeper insights by clarifying questions for respondents or asking follow-up questions.
You can organize the questions logically, with a clear progression from simple to complex, or randomly between respondents. A logical flow helps respondents process the questionnaire easier and quicker, but it may lead to bias. Randomization can minimize the bias from order effects.
Closed-ended, or restricted-choice, questions offer respondents a fixed set of choices to select from. These questions are easier to answer quickly.
Open-ended or long-form questions allow respondents to answer in their own words. Because there are no restrictions on their choices, respondents can answer in ways that researchers may not have otherwise considered.
A questionnaire is a data collection tool or instrument, while a survey is an overarching research method that involves collecting and analyzing data from people using questionnaires.
The third variable and directionality problems are two main reasons why correlation isn’t causation .
The third variable problem means that a confounding variable affects both variables to make them seem causally related when they are not.
The directionality problem is when two variables correlate and might actually have a causal relationship, but it’s impossible to conclude which variable causes changes in the other.
Correlation describes an association between variables : when one variable changes, so does the other. A correlation is a statistical indicator of the relationship between variables.
Causation means that changes in one variable brings about changes in the other (i.e., there is a cause-and-effect relationship between variables). The two variables are correlated with each other, and there’s also a causal link between them.
While causation and correlation can exist simultaneously, correlation does not imply causation. In other words, correlation is simply a relationship where A relates to B—but A doesn’t necessarily cause B to happen (or vice versa). Mistaking correlation for causation is a common error and can lead to false cause fallacy .
Controlled experiments establish causality, whereas correlational studies only show associations between variables.
In general, correlational research is high in external validity while experimental research is high in internal validity .
A correlation is usually tested for two variables at a time, but you can test correlations between three or more variables.
A correlation coefficient is a single number that describes the strength and direction of the relationship between your variables.
Different types of correlation coefficients might be appropriate for your data based on their levels of measurement and distributions . The Pearson product-moment correlation coefficient (Pearson’s r ) is commonly used to assess a linear relationship between two quantitative variables.
A correlational research design investigates relationships between two variables (or more) without the researcher controlling or manipulating any of them. It’s a non-experimental type of quantitative research .
A correlation reflects the strength and/or direction of the association between two or more variables.
Random error is almost always present in scientific studies, even in highly controlled settings. While you can’t eradicate it completely, you can reduce random error by taking repeated measurements, using a large sample, and controlling extraneous variables .
You can avoid systematic error through careful design of your sampling , data collection , and analysis procedures. For example, use triangulation to measure your variables using multiple methods; regularly calibrate instruments or procedures; use random sampling and random assignment ; and apply masking (blinding) where possible.
Systematic error is generally a bigger problem in research.
With random error, multiple measurements will tend to cluster around the true value. When you’re collecting data from a large sample , the errors in different directions will cancel each other out.
Systematic errors are much more problematic because they can skew your data away from the true value. This can lead you to false conclusions ( Type I and II errors ) about the relationship between the variables you’re studying.
Random and systematic error are two types of measurement error.
Random error is a chance difference between the observed and true values of something (e.g., a researcher misreading a weighing scale records an incorrect measurement).
Systematic error is a consistent or proportional difference between the observed and true values of something (e.g., a miscalibrated scale consistently records weights as higher than they actually are).
On graphs, the explanatory variable is conventionally placed on the x-axis, while the response variable is placed on the y-axis.
The term “ explanatory variable ” is sometimes preferred over “ independent variable ” because, in real world contexts, independent variables are often influenced by other variables. This means they aren’t totally independent.
Multiple independent variables may also be correlated with each other, so “explanatory variables” is a more appropriate term.
The difference between explanatory and response variables is simple:
In a controlled experiment , all extraneous variables are held constant so that they can’t influence the results. Controlled experiments require:
Depending on your study topic, there are various other methods of controlling variables .
There are 4 main types of extraneous variables :
An extraneous variable is any variable that you’re not investigating that can potentially affect the dependent variable of your research study.
A confounding variable is a type of extraneous variable that not only affects the dependent variable, but is also related to the independent variable.
In a factorial design, multiple independent variables are tested.
If you test two variables, each level of one independent variable is combined with each level of the other independent variable to create different conditions.
Within-subjects designs have many potential threats to internal validity , but they are also very statistically powerful .
Advantages:
Disadvantages:
While a between-subjects design has fewer threats to internal validity , it also requires more participants for high statistical power than a within-subjects design .
Yes. Between-subjects and within-subjects designs can be combined in a single study when you have two or more independent variables (a factorial design). In a mixed factorial design, one variable is altered between subjects and another is altered within subjects.
In a between-subjects design , every participant experiences only one condition, and researchers assess group differences between participants in various conditions.
In a within-subjects design , each participant experiences all conditions, and researchers test the same participants repeatedly for differences between conditions.
The word “between” means that you’re comparing different conditions between groups, while the word “within” means you’re comparing different conditions within the same group.
Random assignment is used in experiments with a between-groups or independent measures design. In this research design, there’s usually a control group and one or more experimental groups. Random assignment helps ensure that the groups are comparable.
In general, you should always use random assignment in this type of experimental design when it is ethically possible and makes sense for your study topic.
To implement random assignment , assign a unique number to every member of your study’s sample .
Then, you can use a random number generator or a lottery method to randomly assign each number to a control or experimental group. You can also do so manually, by flipping a coin or rolling a dice to randomly assign participants to groups.
Random selection, or random sampling , is a way of selecting members of a population for your study’s sample.
In contrast, random assignment is a way of sorting the sample into control and experimental groups.
Random sampling enhances the external validity or generalizability of your results, while random assignment improves the internal validity of your study.
In experimental research, random assignment is a way of placing participants from your sample into different groups using randomization. With this method, every member of the sample has a known or equal chance of being placed in a control group or an experimental group.
“Controlling for a variable” means measuring extraneous variables and accounting for them statistically to remove their effects on other variables.
Researchers often model control variable data along with independent and dependent variable data in regression analyses and ANCOVAs . That way, you can isolate the control variable’s effects from the relationship between the variables of interest.
Control variables help you establish a correlational or causal relationship between variables by enhancing internal validity .
If you don’t control relevant extraneous variables , they may influence the outcomes of your study, and you may not be able to demonstrate that your results are really an effect of your independent variable .
A control variable is any variable that’s held constant in a research study. It’s not a variable of interest in the study, but it’s controlled because it could influence the outcomes.
Including mediators and moderators in your research helps you go beyond studying a simple relationship between two variables for a fuller picture of the real world. They are important to consider when studying complex correlational or causal relationships.
Mediators are part of the causal pathway of an effect, and they tell you how or why an effect takes place. Moderators usually help you judge the external validity of your study by identifying the limitations of when the relationship between variables holds.
If something is a mediating variable :
A confounder is a third variable that affects variables of interest and makes them seem related when they are not. In contrast, a mediator is the mechanism of a relationship between two variables: it explains the process by which they are related.
A mediator variable explains the process through which two variables are related, while a moderator variable affects the strength and direction of that relationship.
There are three key steps in systematic sampling :
Systematic sampling is a probability sampling method where researchers select members of the population at a regular interval – for example, by selecting every 15th person on a list of the population. If the population is in a random order, this can imitate the benefits of simple random sampling .
Yes, you can create a stratified sample using multiple characteristics, but you must ensure that every participant in your study belongs to one and only one subgroup. In this case, you multiply the numbers of subgroups for each characteristic to get the total number of groups.
For example, if you were stratifying by location with three subgroups (urban, rural, or suburban) and marital status with five subgroups (single, divorced, widowed, married, or partnered), you would have 3 x 5 = 15 subgroups.
You should use stratified sampling when your sample can be divided into mutually exclusive and exhaustive subgroups that you believe will take on different mean values for the variable that you’re studying.
Using stratified sampling will allow you to obtain more precise (with lower variance ) statistical estimates of whatever you are trying to measure.
For example, say you want to investigate how income differs based on educational attainment, but you know that this relationship can vary based on race. Using stratified sampling, you can ensure you obtain a large enough sample from each racial group, allowing you to draw more precise conclusions.
In stratified sampling , researchers divide subjects into subgroups called strata based on characteristics that they share (e.g., race, gender, educational attainment).
Once divided, each subgroup is randomly sampled using another probability sampling method.
Cluster sampling is more time- and cost-efficient than other probability sampling methods , particularly when it comes to large samples spread across a wide geographical area.
However, it provides less statistical certainty than other methods, such as simple random sampling , because it is difficult to ensure that your clusters properly represent the population as a whole.
There are three types of cluster sampling : single-stage, double-stage and multi-stage clustering. In all three types, you first divide the population into clusters, then randomly select clusters for use in your sample.
Cluster sampling is a probability sampling method in which you divide a population into clusters, such as districts or schools, and then randomly select some of these clusters as your sample.
The clusters should ideally each be mini-representations of the population as a whole.
If properly implemented, simple random sampling is usually the best sampling method for ensuring both internal and external validity . However, it can sometimes be impractical and expensive to implement, depending on the size of the population to be studied,
If you have a list of every member of the population and the ability to reach whichever members are selected, you can use simple random sampling.
The American Community Survey is an example of simple random sampling . In order to collect detailed data on the population of the US, the Census Bureau officials randomly select 3.5 million households per year and use a variety of methods to convince them to fill out the survey.
Simple random sampling is a type of probability sampling in which the researcher randomly selects a subset of participants from a population . Each member of the population has an equal chance of being selected. Data is then collected from as large a percentage as possible of this random subset.
Quasi-experimental design is most useful in situations where it would be unethical or impractical to run a true experiment .
Quasi-experiments have lower internal validity than true experiments, but they often have higher external validity as they can use real-world interventions instead of artificial laboratory settings.
A quasi-experiment is a type of research design that attempts to establish a cause-and-effect relationship. The main difference with a true experiment is that the groups are not randomly assigned.
Blinding is important to reduce research bias (e.g., observer bias , demand characteristics ) and ensure a study’s internal validity .
If participants know whether they are in a control or treatment group , they may adjust their behavior in ways that affect the outcome that researchers are trying to measure. If the people administering the treatment are aware of group assignment, they may treat participants differently and thus directly or indirectly influence the final results.
Blinding means hiding who is assigned to the treatment group and who is assigned to the control group in an experiment .
A true experiment (a.k.a. a controlled experiment) always includes at least one control group that doesn’t receive the experimental treatment.
However, some experiments use a within-subjects design to test treatments without a control group. In these designs, you usually compare one group’s outcomes before and after a treatment (instead of comparing outcomes between different groups).
For strong internal validity , it’s usually best to include a control group if possible. Without a control group, it’s harder to be certain that the outcome was caused by the experimental treatment and not by other variables.
An experimental group, also known as a treatment group, receives the treatment whose effect researchers wish to study, whereas a control group does not. They should be identical in all other ways.
Individual Likert-type questions are generally considered ordinal data , because the items have clear rank order, but don’t have an even distribution.
Overall Likert scale scores are sometimes treated as interval data. These scores are considered to have directionality and even spacing between them.
The type of data determines what statistical tests you should use to analyze your data.
A Likert scale is a rating scale that quantitatively assesses opinions, attitudes, or behaviors. It is made up of 4 or more questions that measure a single attitude or trait when response scores are combined.
To use a Likert scale in a survey , you present participants with Likert-type questions or statements, and a continuum of items, usually with 5 or 7 possible responses, to capture their degree of agreement.
In scientific research, concepts are the abstract ideas or phenomena that are being studied (e.g., educational achievement). Variables are properties or characteristics of the concept (e.g., performance at school), while indicators are ways of measuring or quantifying variables (e.g., yearly grade reports).
The process of turning abstract concepts into measurable variables and indicators is called operationalization .
There are various approaches to qualitative data analysis , but they all share five steps in common:
The specifics of each step depend on the focus of the analysis. Some common approaches include textual analysis , thematic analysis , and discourse analysis .
There are five common approaches to qualitative research :
Hypothesis testing is a formal procedure for investigating our ideas about the world using statistics. It is used by scientists to test specific predictions, called hypotheses , by calculating how likely it is that a pattern or relationship between variables could have arisen by chance.
Operationalization means turning abstract conceptual ideas into measurable observations.
For example, the concept of social anxiety isn’t directly observable, but it can be operationally defined in terms of self-rating scores, behavioral avoidance of crowded places, or physical anxiety symptoms in social situations.
Before collecting data , it’s important to consider how you will operationalize the variables that you want to measure.
When conducting research, collecting original data has significant advantages:
However, there are also some drawbacks: data collection can be time-consuming, labor-intensive and expensive. In some cases, it’s more efficient to use secondary data that has already been collected by someone else, but the data might be less reliable.
Data collection is the systematic process by which observations or measurements are gathered in research. It is used in many different contexts by academics, governments, businesses, and other organizations.
There are several methods you can use to decrease the impact of confounding variables on your research: restriction, matching, statistical control and randomization.
In restriction , you restrict your sample by only including certain subjects that have the same values of potential confounding variables.
In matching , you match each of the subjects in your treatment group with a counterpart in the comparison group. The matched subjects have the same values on any potential confounding variables, and only differ in the independent variable .
In statistical control , you include potential confounders as variables in your regression .
In randomization , you randomly assign the treatment (or independent variable) in your study to a sufficiently large number of subjects, which allows you to control for all potential confounding variables.
A confounding variable is closely related to both the independent and dependent variables in a study. An independent variable represents the supposed cause , while the dependent variable is the supposed effect . A confounding variable is a third variable that influences both the independent and dependent variables.
Failing to account for confounding variables can cause you to wrongly estimate the relationship between your independent and dependent variables.
To ensure the internal validity of your research, you must consider the impact of confounding variables. If you fail to account for them, you might over- or underestimate the causal relationship between your independent and dependent variables , or even find a causal relationship where none exists.
Yes, but including more than one of either type requires multiple research questions .
For example, if you are interested in the effect of a diet on health, you can use multiple measures of health: blood sugar, blood pressure, weight, pulse, and many more. Each of these is its own dependent variable with its own research question.
You could also choose to look at the effect of exercise levels as well as diet, or even the additional effect of the two combined. Each of these is a separate independent variable .
To ensure the internal validity of an experiment , you should only change one independent variable at a time.
No. The value of a dependent variable depends on an independent variable, so a variable cannot be both independent and dependent at the same time. It must be either the cause or the effect, not both!
You want to find out how blood sugar levels are affected by drinking diet soda and regular soda, so you conduct an experiment .
Determining cause and effect is one of the most important parts of scientific research. It’s essential to know which is the cause – the independent variable – and which is the effect – the dependent variable.
In non-probability sampling , the sample is selected based on non-random criteria, and not every member of the population has a chance of being included.
Common non-probability sampling methods include convenience sampling , voluntary response sampling, purposive sampling , snowball sampling, and quota sampling .
Probability sampling means that every member of the target population has a known chance of being included in the sample.
Probability sampling methods include simple random sampling , systematic sampling , stratified sampling , and cluster sampling .
Using careful research design and sampling procedures can help you avoid sampling bias . Oversampling can be used to correct undercoverage bias .
Some common types of sampling bias include self-selection bias , nonresponse bias , undercoverage bias , survivorship bias , pre-screening or advertising bias, and healthy user bias.
Sampling bias is a threat to external validity – it limits the generalizability of your findings to a broader group of people.
A sampling error is the difference between a population parameter and a sample statistic .
A statistic refers to measures about the sample , while a parameter refers to measures about the population .
Populations are used when a research question requires data from every member of the population. This is usually only feasible when the population is small and easily accessible.
Samples are used to make inferences about populations . Samples are easier to collect data from because they are practical, cost-effective, convenient, and manageable.
There are seven threats to external validity : selection bias , history, experimenter effect, Hawthorne effect , testing effect, aptitude-treatment and situation effect.
The two types of external validity are population validity (whether you can generalize to other groups of people) and ecological validity (whether you can generalize to other situations and settings).
The external validity of a study is the extent to which you can generalize your findings to different groups of people, situations, and measures.
Cross-sectional studies cannot establish a cause-and-effect relationship or analyze behavior over a period of time. To investigate cause and effect, you need to do a longitudinal study or an experimental study .
Cross-sectional studies are less expensive and time-consuming than many other types of study. They can provide useful insights into a population’s characteristics and identify correlations for further research.
Sometimes only cross-sectional data is available for analysis; other times your research question may only require a cross-sectional study to answer it.
Longitudinal studies can last anywhere from weeks to decades, although they tend to be at least a year long.
The 1970 British Cohort Study , which has collected data on the lives of 17,000 Brits since their births in 1970, is one well-known example of a longitudinal study .
Longitudinal studies are better to establish the correct sequence of events, identify changes over time, and provide insight into cause-and-effect relationships, but they also tend to be more expensive and time-consuming than other types of studies.
There are eight threats to internal validity : history, maturation, instrumentation, testing, selection bias , regression to the mean, social interaction and attrition .
Internal validity is the extent to which you can be confident that a cause-and-effect relationship established in a study cannot be explained by other factors.
In mixed methods research , you use both qualitative and quantitative data collection and analysis methods to answer your research question .
The research methods you use depend on the type of data you need to answer your research question .
A confounding variable , also called a confounder or confounding factor, is a third variable in a study examining a potential cause-and-effect relationship.
A confounding variable is related to both the supposed cause and the supposed effect of the study. It can be difficult to separate the true effect of the independent variable from the effect of the confounding variable.
In your research design , it’s important to identify potential confounding variables and plan how you will reduce their impact.
Discrete and continuous variables are two types of quantitative variables :
Quantitative variables are any variables where the data represent amounts (e.g. height, weight, or age).
Categorical variables are any variables where the data represent groups. This includes rankings (e.g. finishing places in a race), classifications (e.g. brands of cereal), and binary outcomes (e.g. coin flips).
You need to know what type of variables you are working with to choose the right statistical test for your data and interpret your results .
You can think of independent and dependent variables in terms of cause and effect: an independent variable is the variable you think is the cause , while a dependent variable is the effect .
In an experiment, you manipulate the independent variable and measure the outcome in the dependent variable. For example, in an experiment about the effect of nutrients on crop growth:
Defining your variables, and deciding how you will manipulate and measure them, is an important part of experimental design .
Experimental design means planning a set of procedures to investigate a relationship between variables . To design a controlled experiment, you need:
When designing the experiment, you decide:
Experimental design is essential to the internal and external validity of your experiment.
I nternal validity is the degree of confidence that the causal relationship you are testing is not influenced by other factors or variables .
External validity is the extent to which your results can be generalized to other contexts.
The validity of your experiment depends on your experimental design .
Reliability and validity are both about how well a method measures something:
If you are doing experimental research, you also have to consider the internal and external validity of your experiment.
A sample is a subset of individuals from a larger population . Sampling means selecting the group that you will actually collect data from in your research. For example, if you are researching the opinions of students in your university, you could survey a sample of 100 students.
In statistics, sampling allows you to test a hypothesis about the characteristics of a population.
Quantitative research deals with numbers and statistics, while qualitative research deals with words and meanings.
Quantitative methods allow you to systematically measure variables and test hypotheses . Qualitative methods allow you to explore concepts and experiences in more detail.
Methodology refers to the overarching strategy and rationale of your research project . It involves studying the methods used in your field and the theories or principles behind them, in order to develop an approach that matches your objectives.
Methods are the specific tools and procedures you use to collect and analyze data (for example, experiments, surveys , and statistical tests ).
In shorter scientific papers, where the aim is to report the findings of a specific study, you might simply describe what you did in a methods section .
In a longer or more complex research project, such as a thesis or dissertation , you will probably include a methodology section , where you explain your approach to answering the research questions and cite relevant sources to support your choice of methods.
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A cross-sectional study involves the review of information from a population demographic at a specific point in time. The participants who get involved with this research are selected based on particular variables that researchers want to study. It is often used in developmental psychology, but this method is also useful in several other areas. Social sciences and educational processes benefit from this work.
Researchers who are following cross-sectional study techniques would study select groups of people in different age demographics. Their work would look at one investigatory point at a time. By taking this approach, any differences that exist between the demographics would be attributed to characteristics instead of something that happens.
These studies are observational in nature. They are sometimes described as descriptive research, but not causal or relational. That means researchers are unable to determine the cause of something, such as an illness, when using this method.
Several advantages and disadvantages are worth considering when looking at cross-sectional studies.
1. This study takes place during a specific moment in time. A cross-sectional study has defined characteristics that limit the size and scope of the work. Researchers look at specific relationships that happened during a particular moment in time. That means there are fewer risks to manage if tangents begin to develop in the data. The goal is to look for a meaningful result within an expected boundary.
2. No variable manipulation occurs with a cross-sectional study. Researchers directly observe the variables under study when using the cross-sectional technique. There is no reason to manipulate the environment because this is not an experimental technique. The data gathering process goes quickly because everything occurs within the scope of the research method. This advantage reduces the risk of having bias creep into the information being gathered.
3. It is an affordable way to conduct research. A cross-sectional study is much more affordable to complete when compared to the other options that are available to researchers today. No follow up work is necessary when taking this approach because once the information gets collected from the entire participant group, it can be analyzed immediately. This advantage as possible because only a single time reference is under consideration.
This approach allows for usable data to become available without the risk of a significant initial investment. Most of the data points collected using this method come from self-report surveys. Researchers can then collect a significant amount of information from a large pool of participants without a major time investment.
4. This study method provides excellent controls over the measurement process. Cross-sectional studies are only as good as the measurement processes that researchers used to collect data. Because there aren’t any long-term considerations involved with this specific approach, researchers have more control over the information acquisition process. Everything obtained during this work is quickly and easily measured and applied to the targeted demographics because the controls involved are straightforward to implement.
5. Researchers can look at several useful characteristics at once. Many researchers prefer the cross-sectional studies method because it allows them to look at numerous characteristics simultaneously. Instead of focusing on income, gender, age, or other separating factors, this method looks at each participant as an entire individual. That makes it possible for the work to include several useful characteristics that can each benefit from changing variables instead of using only one to determine an outcome.
This advantage is the reason why researchers often use cross-sectional studies to look at the prevailing characteristics in a given population. It is a process that lets different variables become the foundation of new correlations.
6. It provides relevant information in real-time updates. Cross-sectional studies provide us with a snapshot of a specific group of people at a particular point in time. Unlike other methods of research that look at demographics over an extended period, we use this information to look at what is happening in the present. That means the data researchers collect from this process is immediately relevant, giving us an opportunity to create real-time updates within specific population groups.
This process is how we can determine if there are specific risk factors that correlate to particular outcomes wit in that group. A cross-sectional study might look at a person’s past smoking and chewing habits to determine if there is a correlation with a recent lung cancer diagnosis. Although it won’t provide a cause-and-effect explanation, it does offer a fast look at potential correlations.
7. Cross-sectional studies miss fewer data points. The processes involved with cross-sectional studies reduce the risk of missing critical data points. Researchers have the ability to maximize their examination of the available information at any time because there are no time variables included in this work. That means a lower error rate typically occurs when using this method compared to the other approaches that are available to the scientific community.
8. It allows anyone to look at the data to determine a possible conclusion. The information that cross-sectional studies obtain is always suitable for secondary analysis. This advantage means that researchers can collect information for one set of purposes, and then use it to explore different variables that might exist in that specific demographic at the same time. That means an investment in this work can provide ongoing usefulness because it always applies to the people involved during that specific time. It is one of the easiest ways to maximize your research investment value.
9. Cross-sectional studies offer information that’s well-suited for descriptive analysis. If researchers want to develop a general hypothesis, then cross-sectional studies are the best way to generate specific situations that face a particular demographic. Each description of the critical data points creates the possibility of forwarding movement toward a future solution that may not have been considered previously.
Although this benefit doesn’t apply to causal relationships with this research method, the information collected from cross-sectional studies is a useful forward push toward additional research.
10. The focus of a cross-sectional study is to prove or disprove an assumption. A cross-sectional study is a research tool that is useful across various industries. The reason why it is such a generalized process that anyone can initiate is that the purpose of the work is to prove or disapprove and assumption or theory. Although health-related work tends to be the most popular industry that takes advantage of this approach, retail, education, social science, religion, and government industries can also benefit from this process.
The research that occurs allows each industry to learn more about the various demographics for the purpose of analyzing a target market. It creates data that’s useful when trying to determine what products or services to sell, or when it is necessary to look for specific patient outcomes.
1. It requires the entire population to be studied to create useful data. A correctly structured cross-sectional study must be representative of an entire demographic for it to provide useful information. If this representation is not possible, then the data collected from the participating individuals will have a built-in error rate that must come under consideration.
That’s why a complete generalization is not possible when using this approach. Environmental conditions, a person’s education, and several other factors can all change an individual’s perspective.
2. A researcher’s personal bias can influence the data from cross-sectional studies. Everyone has particular biases that influence their personality and general perspective on life. Many of these circumstances come from the conditioning that happens over the course of time. Even people who work hard to avoid showing bias in any situation can come under the influence of this disadvantage of cross-sectional studies.
Some demographics might include prison populations, the homeless, or people who are unable to leave their homes. If a researcher feels uncomfortable contacting individuals in these groups, then the final data points will not have as much relevance as they could.
3. The questions asked during cross-sectional studies may lead to specific results. If researchers want to achieve a specific result when performing a cross-sectional study, then they can ask questions in such a way that it leads participants to the desired answer. When there are surveys or questionnaires about specific aspects of a person’s life, then the answers received may not always result in an accurate report. Shared experiences can result in different perspectives.
We have seen this disadvantage play out numerous times throughout several generations. The people who were alive during the Vietnam war, the attack on Pearl Harbor, or the terrorist event in New York City on 9/11 have shared experiences that make them different from other age groups. The people who survived these events are another subgroup that can impact the quality of information gathered.
4. Large sample sizes are often necessary to generate usable information. A significant sample size is often necessary for a cross-sectional study to provide useful information. This disadvantage occurs because the entire population demographic must go through the research at once to prevent errors in the data. When a smaller sample size is the focus of the work, then the risk of errors entering into the information increases dramatically. There are more opportunities for coincidence or a chance to influence the results with a smaller research sample.
Although cross-sectional studies are often very affordable, the inclusion of an entire demographic pushes the cost of this work higher than it would be for other approaches.
5. Cross-sectional studies don’t offer any control over purpose or choice. When the data from a cross-sectional study is found useful for secondary data analysis, the bias of the researchers can influence the information without any future realization. The secondary approach has no control over how this work gets completed initially. That’s why an overview of the methods used and the purpose for collecting information in the first place are often included as part of the results of this work.
If these additional facts are not part of the final experience, and the usefulness of the information for future needs becomes questionable.
6. No information about causal relationships is possible with this approach. This research method does not provide information about causal relationships. The goal of this approach is to offer correlated data that is useful when drawing conclusions about a specific demographic. It can only let researchers see that a causal relationship exists without letting them know the reason behind its existence.
That’s why individualization is a disadvantage to this type of study. Researchers are wanting to see a generalized overview of a specific population sample instead of understanding why some people make particular choices.
7. Demographic definitions must be available to create a. successful result. The information collected during a cross-sectional study is not reliable unless there are specific definitions in place for a population sample that is large enough for generalization. If researchers want to look at a rare outcome or a unique event, then inappropriate conclusions could get gleaned from the collected data. Trying to force a specific question or result could encourage responses that are unnecessary within the study population.
The only way to avoid this disadvantage of a cross-sectional study is to create definitions that work specifically with the intended results.
8. Cross-sectional studies have no way to measure incidence. The goal of a cross-sectional study is to review the data that researchers collect as they study-specific variables. It does not take a look at the reason why the specific information points occur within the population demographics. This disadvantage limits the availability of an outcome for researchers in many situations because there is no determination available as to why the variables are present initially.
It only measures the existence and relationships that are present in that environment, not what triggers the variables.
9. It can be challenging to duplicate the results. Even though a large population sample is necessary to create an accurate dataset from a cross-sectional study, it is challenging to duplicate results from multiple efforts. This disadvantage occurs because work happens in real-time situations. What happens right now can create a very different result then what could happen in the future.
That’s why many institutions face some challenges when they attempt to put together a sampling pool. The variables that should be studied are available in complex ways that may be difficult to manage. This issue is so detrimental that the timing of a specific snapshot is never a 100% guarantee that it’s representative of the entire population group.
A cross-sectional study is a useful research tool in most areas of health and wellness. When we can learn more about what is happening within a specific population demographic, then researchers can better understand the relationships that could exist between particular variables. The information that comes out of this process allows us to develop further studies that can explore the results in greater depth.
Several other research study options are available when there is a need to collect information from a specific demographic. It is essential to compare the critical points from each approach to determine what the best possible solution will be for each situation.
These cross-sectional advantages and disadvantages show us that a massive undertaking of simultaneous data collection can provide unique results that can benefit an entire population group. Although there are some challenges to manage when taking this approach, it is one that most researchers find to be beneficial.
by Kate Pettitt | Mar 25, 2021 | Earthworks , Tutorial
Previously, in regard to earthworks estimation, we have written two articles on the Cross Section and Grid Methods. Read these in our Industry Articles library.
This article demonstrates how to calculate earthworks cut and filling using the Cross Section Method and a spreadsheet. Starting with pen and paper we will show you how to generate and input the cross section data to calculate the cut and fill volumes in the spreadsheet. (There is a separate blog which explains how to use the Grid Method sheet)
Download the spreadsheet to use with the tutorial.
The cross-section method is when you divide your site into equal parallel sections. Imagine slicing through the earth with a knife at regular intervals.
For each cross section the cut area and the fill area are calculated. Then for each cross section pair, the cut and fill volume of the section between them is approximated by finding the average of two adjacent sections and multiplying by the distance between them.
An example of a cross sections and sums done to calculate the volume is below:
The formula to calculate the volume between two sections:
Average Cut Area = (4295 + 2565)/2 = 3430m sq
Average Fill Area = (5376 + 5906)/2 = 5641m sq
Distance Between Sections = 50m
Cut Volume = 3430 x 50 = 171,500m cu
Fill Volume = 5641 x 50 = 282,050m cu
For the whole site, the total volume is determined by adding all the pairs of cut volumes and the fill volumes together.
As there are so many calculations to complete, another method is using a spreadsheet, such as the one we have provided.
The spreadsheet :
a) Creates a graph showing the profile of the Existing and Proposed for each section. This shows the existing levels in blue and proposed in orange.
b) Calculates the cut and fill area for each section. Shown next to the profile graph.
c) Calculates the overall total Cut, Fill and Net Volume. Shown in the Results table.
4. Collect your data. You now need to take off the existing (E) and proposed (P) levels and write them next to each significant change in elevation, to produce a cross section. An example, showing one way to do this, is in the photo. It is key to use your fine pen or pencil here to ensure you can fit in the two levels and so they remain legible.
In this example, the levels have been defined using contour lines.
i) For each contour make a mark on your section and write the level.
I have used two colours to make the mark; black for existing and written the level above the section line and pink for the proposed and the level is written below the line. This makes it clear for when you are entering the levels into the spreadsheet.
ii) The start of the section is 0 distance and then you measure from 0 along the line to get the distance for the change in elevation. The distances for the changes for the existing may well be different to the proposed.
You can use a ruler to measure the distance in cm/mm/inches and then multiple by x to scale it. Alternatively, you can use a scale ruler with a compatible level which means you don’t need to complete that sum – really handy!
TOP TIPS : 1. Use a fine line pen or mechanical pencil so that your figures for each level change remain legible in the small space that you have available to you.
2. Use a roller ruler to draw parallel lines at set distances
3. Use a scale ruler, with a compatible scale
1. Open the spreadsheet and select the “Section Method Example” tab so that you have the sheet on screen.
You will notice that this sheet is protected and cannot be amended. Before starting your own sheet, we recommend you view this example to understand what your finished cross section results should look like.
2. Open the second tab called, “Section Method”. This one you can edit and enter your data into. (Please refer to the licence tab for modifying and redistributing terms.)
5. Read your Results and make your estimations. Once all data has been entered, you will have the Cut, Fill Volumes calculated in each section and the Total volumes net volume for the entire grids.
You can now use this data to estimate the cost of your project.
1. Check every section for data entry mistakes
2. The graphs will highlight an major anomalies
Although the Grid Method spreadsheet does speed up the calculation process, the possibility of human error when inputting the data remains. The alternative to using the spreadsheet is to allow TIN prism software to complete the calculations for you.
Kubla Cubed calculates cut and fill volumes using TIN (Triangular Irregular Networks), which will calculate to a higher degree of accuracy than the 2D grid or cross section methods, and in less time.
Click below to find out more and download a free version of Kubla Cubed (Lite)
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Course: ap®︎/college calculus ab > unit 8, volume with cross sections: intro.
Rogowski-coil (RC) current sensors are preferred for their ability to measure a broad range of currents, maintain linearity, and avoid magnetic saturation. This paper describes the design process and testing of RC for high frequency signal. The focus of the paper is on designing of the RC, which is modelled in 3D using Ansys Maxwell and experimental setup for testing purpose. Finite element method (FEM) is adapted to measure parameters of RC and the same is verified with experiment. A rectangular cross section model of RC is developed with nonmagnetic core. The electrical parameters of the coil are theoretically calculated using a lumped model, also frequency response of RC for different terminal resistance is analysed. The performance of the RC is experimentally tested for currents of 25 mA and 60 mA peak at a frequency of 100 kHz. The electrical parameters and output of the RC are examined and analysed through theoretical, FEM, and experimental method. The effect of terminal resistance on output of RC is analysed. The measured RC output voltage is compared and validated with FEM simulation result for peak current 25 mA and 60 mA at a 100 kHz frequency. Further, the performance of RC is analysed using the FEM method for 25 mA and 60 mA(peak) sinusoidal current at different frequency such as 100 kHz, 500 kHz and 1 MHz with terminal resistance of 1Ω and 10Ω and its results are reported. The sensitivity of prototype RC model is also analysed and its result is closely matched well with FEM simulation results.
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Shafiq, M.; Stewart, B.G.; Hussain, G.A.; Hassan, W.; Choudhary, M.; Palo, I.: Design and applications of Rogowski coil sensors for power system measurements: a review. Measur. J. Int. Measure. Confed. 203 , 112014 (2022). https://doi.org/10.1016/j.measurement.2022.112014
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Bawankule, P., Chandrasekaran, K. Modeling and Designing of Rogowski Coil for High-Frequency Sinusoidal Signal Measurement with Finite Element and Experimental Method. Arab J Sci Eng (2024). https://doi.org/10.1007/s13369-024-09410-x
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Revised on June 22, 2023. A cross-sectional study is a type of research designin which you collect data from many different individuals at a single point in time. In cross-sectional research, you observe variableswithout influencing them. Researchers in economics, psychology, medicine, epidemiology, and the other social sciences all make use of ...
Cross-sectional study design is a type of observational study design. In a cross-sectional study, the investigator measures the outcome and the exposures in the study participants at the same time. ... The OR (as discussed in the earlier methodology series - II case-control studies) is AD/BC or 50*90/10*150. Thus, the OR is 3.0. The ...
Cross-Sectional vs. Longitudinal. A cross-sectional study design is a type of observational study, or descriptive research, that involves analyzing information about a population at a specific point in time. This design measures the prevalence of an outcome of interest in a defined population. It provides a snapshot of the characteristics of ...
A cross-sectional study is a type of research design in which you collect data from many different individuals at a single point in time. In cross-sectional research, you observe variables without influencing them. Researchers in economics, psychology, medicine, epidemiology, and the other social sciences all make use of cross-sectional studies ...
Cross-Sectional vs. Longitudinal Studies . Cross-sectional research differs from longitudinal studies in several important ways. The key difference is that a cross-sectional study is designed to look at a variable at a particular point in time. A longitudinal study evaluates multiple measures over an extended period to detect trends and changes.
This paper describes the cross-sectional design, examines the strengths and weaknesses, and discusses some methods to report the results. ... Observational research methods—Cohort studies, cross-sectional studies, and case-control studies. African Journal of Emergency Medicine, 2 (1), 38-46. doi: 10.1016/j.afjem.2011.12.004 ...
A cross-sectional study is an experimental design that analyzes data from a representative sample at a specific point in time. Researchers usually evaluate multiple attributes at once when using this design. Unlike longitudinal studies, these studies don't track changes over time. These studies are a snapshot of a moment in time.
In medical research, epidemiology, social science, and biology, a cross-sectional study (also known as a cross-sectional analysis, transverse study, prevalence study) is a type of observational study that analyzes data from a population, or a representative subset, at a specific point in time—that is, cross-sectional data. [definition needed]In economics, cross-sectional studies typically ...
The weaknesses of cross-sectional studies include the inability to assess incidence, to study rare diseases, and to make a causal inference. Unlike studies starting from a series of patients, cross-sectional studies often need to select a sample of subjects from a large and heterogeneous study population. Thus, they are susceptible to sampling ...
Cross-sectional studies look at a population at a single point in time, like taking a slice or cross-section of a group, and variables are recorded for each participant. ... Methodology Series Module 3: Cross-sectional Studies. Indian journal of dermatology, 61(3), 261-264. doi: 10.4103/0019-5154.182410.
A cross-sectional study provides valuable insights into a population's characteristics, attitudes, and behaviors at a single point in time. As with any research design, cross-sectional studies should be used with other research methods to provide a complete study. Overall, cross-sectional studies can be a valuable tool for researchers looking ...
Abstract. Cross-sectional study design is a type of observ ational study design. In a cross-sectional study, the investigator measur es the outcome and th e exposures in the study participan ts at ...
3.1. Strengths: when to use cross-sectional data. The strengths of cross-sectional data help to explain their overuse in IS research. First, such studies can be conducted efficiently and inexpensively by distributing a survey to a convenient sample (e.g., the researcher's social network or students) (Compeau et al., 2012) or by using a crowdsourcing website (Lowry et al., 2016, Steelman et ...
A cross-sectional study is a research methodology that involves collecting data on a sample of individuals at one specific point in time. The researcher (s) will collect data on various factors, all at the one time, and observe how those variables are related to other factors. In this type of study, researchers do not manipulate any variables ...
A cross-sectional study is a method of research that takes a snapshot of a single point in time to see what variables are present in that population. Major characteristics of a cross-sectional ...
They are useful for establishing preliminary evidence in planning a future advanced study. This article reviews the essential characteristics, describes strengths and weaknesses, discusses methodological issues, and gives our recommendations on design and statistical analysis for cross-sectional studies in pulmonary and critical care medicine.
Longitudinal studies and cross-sectional studies are two different types of research design. In a cross-sectional study you collect data from a population at a specific point in time; in a longitudinal study you repeatedly collect data from the same sample over an extended period of time. Longitudinal study.
In medical research, a cross-sectional study is a type of observational study design that involves looking at data from a population at one specific point in time. In a cross-sectional study, investigators measure outcomes and exposures of the study subjects at the same time. It is described as taking a "snapshot" of a group of individuals.
Cross-sectional research studies are a type of descriptive research that provides information from groups. Because it is a snapshot of a moment in time, this type of research cannot be used to ...
7. Cross-sectional studies miss fewer data points. The processes involved with cross-sectional studies reduce the risk of missing critical data points. Researchers have the ability to maximize their examination of the available information at any time because there are no time variables included in this work.
The cross-section method is when you divide your site into equal parallel sections. Imagine slicing through the earth with a knife at regular intervals. For each cross section the cut area and the fill area are calculated. Then for each cross section pair, the cut and fill volume of the section between them is approximated by finding the ...
In the video we are told that each cross section (parallel to the 𝑦-axis) of the 3-dimensional object is a square. 𝑓 (𝑥) − 𝑔 (𝑥). Thereby the area of this cross section is (𝑓 (𝑥) − 𝑔 (𝑥))². In the practice problems the cross sections likely have other shapes and you'll have to define the area differently.
Variable cross-section feature of the composite laminate was considered. Local ply density matrix method was introduced to characterize ply drop-off. Proposed method was validated by cantilever beam bending experiment. Inner and outer ply drop-off models were compared by the proposed method.
Furthermore, we extend the range of electron angles and energies over which theoretical data are available for the doubly differential cross section for ionization. This provides strong evidence that at the level of doubly differential cross sections nonperturbative high-order methods are required to accurately model the ionization process.
The focus of the paper is on designing of the RC, which is modelled in 3D using Ansys Maxwell and experimental setup for testing purpose. Finite element method (FEM) is adapted to measure parameters of RC and the same is verified with experiment. A rectangular cross section model of RC is developed with nonmagnetic core.