Which statement best describes when relative risk or odds ratio is most appropriately used in study designs?

• A. Relative risk is the ratio of incidence in exposed vs unexposed groups and is used in cohort studies.
• B. Odds ratio is the odds of exposure among cases relative to controls and is used in case-control studies or logistic regression; for rare diseases OR approximates RR.
• C. Relative risk and odds ratio are interchangeable in all study designs.
• D. Relative risk is measured in cross-sectional studies only.

Answer: (B)