The hallmark feature of an analytic epidemiologic study is the use of an appropriate comparison group.
Analytic epidemiology is the study concerned with tracking causes and effects, or the why and the how of a particular disease. Epidemiologists use analytic epidemiology to define the relationship between exposures and effects and to test assumptions about causal relationships.
Comparison groups are very important in an epidemiologic study they are used to approximate the counterfactual data defining how the disease would have progressed without the intervention. The more similar that comparison group is to the subject group, the stronger the evaluation can be.
