What is the primary characteristic of a case-control study?

A case-control study is primarily characterized by its retrospective nature, meaning it looks backward to assess prior exposures among individuals. In this type of study, researchers identify individuals who have a specific condition or outcome (cases) and compare them to individuals without that condition (controls). The goal is to determine if there is an association between prior exposures or risk factors and the outcome of interest.

This backward-looking approach allows researchers to investigate factors that may have contributed to the condition by examining past behaviors, exposures, or risk factors in both groups. The findings can help establish potential links between exposure and outcomes, although they do not provide direct information about incidence or risk ratios typically associated with cohort studies.

In a case-control study, the focus is not on measuring incidence or conducting randomized experiments, as these are characteristics associated with other types of studies, such as cohort studies and randomized controlled trials. Thus, the correct answer accurately describes the key characteristic that defines a case-control study.