A
case-control study is a type of
study design used widely, originally developed in
epidemiology, although its use has also been advocated for the social sciences. It is a type of
observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute. Case-control studies are often used to identify factors that may contribute to a medical condition by comparing subjects who have that condition/disease (the "cases") with patients who do not have the condition/disease but are otherwise similar (the "controls"). They require fewer resources but provide less evidence for causal inference than a
randomized controlled trial.