In a case-control study of 200 cases and 200 controls, 120 cases and 60 controls were exposed to a risk factor. The appropriate measure of association is:
- A Odds ratio ✓
- B Attributable risk
- C Relative risk
- D Incidence rate
Correct answer: A. Odds ratio
Explanation
Case-control studies cannot directly calculate incidence or relative risk because subjects are selected based on outcome status. The odds ratio is the appropriate measure, calculated as (120/80) divided by (60/140) equals 3.5. Relative risk and incidence require cohort studies or cross-sectional designs. Attributable risk also requires incidence data.
Reference: Park's Textbook of Preventive and Social Medicine, 26th ed.
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