What is a case-control study?

A case-control study is an observational study design primarily used in epidemiology to identify and compare individuals who have a specific condition (the case group) with those who do not have the condition (the control group). This approach allows researchers to explore potential associations between exposures or risk factors and outcomes of interest.

In this type of study, cases are identified based on the presence of the condition, while controls are selected based on their absence of the condition. This comparative framework is designed to determine whether there are any significant differences in exposure to certain risk factors between the two groups, helping to establish possible links between an exposure and the development of the condition.

The other options describe different types of research methodologies or study designs. For instance, measuring outcomes before and after treatment relates to cohort studies or intervention studies, while randomized controlled trials involve the random assignment of subjects to different treatment groups to ascertain efficacy. Additionally, a study that collects data on a large number of variables typically refers to observational studies like cross-sectional studies or surveys, rather than the specific comparative nature of case-control studies.