What statistical measure is commonly used in case-control studies?

In case-control studies, the odds ratio is the statistical measure commonly used to compare exposure odds between cases (those with the outcome of interest) and controls (those without the outcome). This is because case-control studies are retrospective in nature; they start with the outcome and look back to determine exposure status.

The odds ratio quantifies the strength of association between an exposure and an outcome, allowing researchers to determine how much more likely cases are to have been exposed compared to controls. It is calculated by taking the ratio of the odds of exposure in the cases to the odds of exposure in the controls. This measure is particularly useful in situations where the outcome is rare, as it provides insight into potential risk factors without requiring the establishment of incidence rates that are typical in cohort studies.

Relative risk, on the other hand, is generally used in cohort studies where the incidence of an outcome can be observed directly over time. Absolute risk pertains to the actual probability of the event occurring in a particular group and is less commonly applied in case-control designs. The mean difference is generally used in contexts involving continuous variables rather than categorical outcomes found in case-control studies.