Which statement best distinguishes confounding from effect modification in epidemiology?

Which statement best distinguishes confounding from effect modification in epidemiology?

• A. Confounding occurs when an extraneous variable is associated with both exposure and outcome, distorting the association.
• B. Effect modification occurs when the exposure-outcome association varies by levels of another variable.
• C. A mediator explains the causal pathway between exposure and outcome.
• D. Effect modification eliminates the association between exposure and outcome.

Answer: (A)