A study shows that coffee drinkers have more lung cancer, but the coffee drinkers are more often smokers. What is smoking in this context?
Answer and explanation
Correct answer: A. A confounder
- Step 1: A confounder is associated with both the exposure and the outcome and is not on the causal pathway. Step 2. It distorts the apparent relationship, and can be handled by restriction, stratification or multivariable adjustment. Answer: A confounder. Why not the others: An effect modifier changes the size of the effect in subgroups. Coffee does not cause smoking, so smoking is not a mediator. Recall bias is about reporting.
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