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

A case-control study is designed to retrospectively compare individuals who have a specific disease or condition (the cases) with individuals who do not have the disease (the controls). This design characteristic allows researchers to identify potential risk factors or associations that may contribute to the disease. By looking back in time at prior exposures or characteristics of both groups, researchers can gather insights into factors that may be linked to the onset of the disease. This type of study is particularly useful in understanding rare diseases as it allows for the examination of a smaller, more targeted group of individuals affected by the disease compared to the larger general population.

The other options do not align with the characteristics of a case-control study. A cohort study, for example, follows a group of individuals over time, which is not retrospective. Random sampling of the general population is more aligned with cross-sectional study designs, while including only healthy individuals is not representative of a case-control study where both affected and unaffected individuals are compared to understand the disease's context. Thus, the key characteristic that defines a case-control study is its retrospective comparative approach between those with and without a disease.