Which study design primarily uses odds ratio?

• A. Case-control studies
• B. Randomized controlled trials
• C. Cohort studies
• D. Cross-sectional studies

Answer: (A)

Odds ratio is the measure that best fits case-control designs because these studies start by selecting people based on disease status, so you don’t have information on the overall risk or incidence of disease in exposed versus unexposed groups. Instead, you compare how common exposure is among cases (those with the disease) to how common exposure is among controls (those without the disease). The odds ratio captures this association directly from that sampling scheme. When the disease is rare, the odds ratio closely approximates the relative risk, which makes interpretation straightforward. In contrast, randomized trials and cohort studies provide incidence data that lets you compute risk ratios (relative risk) more directly, while cross-sectional studies often focus on prevalence and can use odds ratios for associations as well, but the design most primarily associated with using odds ratio as the main measure is case-control.