For a variable to confound an observed association between alcohol consumption and oesophageal cancer, it must fulfil all of the following conditions EXCEPT one. Identify the condition that is NOT required:
- A It must be associated with the exposure in the source population
- B It must be statistically significantly associated with the outcome in the study sample ✓
- C It must not be an intermediate step in the causal pathway between exposure and outcome
- D It must be an independent risk factor for the outcome
Correct answer: B. It must be statistically significantly associated with the outcome in the study sample
Explanation
Confounding requires association with the exposure, independent association with the outcome, and exclusion from the causal pathway. Statistical significance in the particular study sample is not a requirement; confounding can be substantial yet nonsignificant in small samples, and it is judged by change in the effect estimate on adjustment, conventionally more than 10 percent, not by p values. Options A, D and C are the classical triad of confounder criteria.
Reference: Gordis Epidemiology, 6th ed.
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