Study design used to identify factors that may contribute to a medical condition by comparing a group of patients who have that condition (experimental group) with a group of patients who do not (control group).
An Inquiry in which groups of individuals are selected because they do (the cases) or do not (the controls) have the disease whose cause and other attributes are being studied; the groups are then compared with respect to their past, existing, or future characteristics judged likely to be relevant to the disease to see which of the characteristics differ, and how, in the cases as compared to the controls.
Comparison of a group of people who have a disease with another group free from that disease, in terms of variables in their backgrounds (e.g. cigarette smoking in those who have died from lung cancer and in those dying from other causes). In the more precise matched pair study every individual with the disease is paired with a control matched on the basis of (say) age, sex, or occupation in order to place greater emphasis on a factor for which the pairs have not been matched. Compare cohort study, cross-sectional study.