Identify the confounding variable in a study where diet quality affects both participation and health outcomes.

• A. Age
• B. Diet quality
• C. Gender
• D. Training intensity

Answer: (B)

A confounding variable is something that influences both the exposure and the outcome, creating a false impression of a link between them. In this study, diet quality affects whether people participate and also affects health outcomes. Because diet quality is related to participation and independently related to health, it can distort the apparent effect of participation on health. If you don’t account for diet quality, you might incorrectly conclude that participation alone drives health differences when, in fact, healthier individuals are simply more likely to participate and to have better health outcomes due to their diet. By adjusting for diet quality—through stratification, covariate adjustment, or matching—you get a clearer view of the true effect of participation on health.