In a case-control study of oral contraceptives and venous thrombosis, investigators match controls to cases on age and parity before analyzing the data. The principal purpose of this matching is to:

• A Convert the study into a quasi-experimental design
• B Increase the statistical power to detect a causal effect of oral contraceptives themselves
• C Ensure the sample is representative of the source population
• D Eliminate confounding by age and parity at the design stage ✓

Explanation

Matching in case-control studies is a technique to control confounding by ensuring comparable distribution of selected confounders between cases and controls. It does not improve power for the main exposure, since matched pairs concordant on the exposure contribute nothing to the comparison, and it never makes the observational design experimental. Representativeness of controls depends on how they are selected from the source population, not on matching. Overmatching on variables in the causal chain can even obscure a true association.

Reference: Gordis Epidemiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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