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Quizzes

Quiz 7, Module Confounding

7. What if, during data analysis, investigators found that use of vitamin supplementation was associated with pesticide use and was an independent risk factor for breast cancer? Should they attempt to control for this potential confounder?

  1. Yes, investigators should control for vitamin supplementation as they did for other potential confounders and add this variable to the list of hypothesized confounders in the Methods section of the paper.
  2. Yes, investigators should control for vitamin supplementation and describe the process of confounder selection in their Results section.
  3. No, it is inappropriate to control for variables if they were not hypothesized as confounders a priori.
Answer (a) — incorrect: Many variables may act as confounders in one study. While it is important to hypothesize which factors may confound an association, it is also important to evaluate other potential confounders during the analyses as well. In doing so, you must report the process of how you selected potential confounders (i.e., a priori confounders in the Methods section and a posteriori confounders in the Results section), and discuss your findings in the Discussion section.
Answer (b) — correct: It is important to report the selection process of confounding variables in your work. A priori confounders should be reported in the Methods section, a posteriori confounders in the Results section.
Answer (c) — incorrect: It is not always possible to know all potential confounders at the beginning of a study. This may happen when investigating an exposure-disease association which has not been studied well, or if cost and feasibility make it impossible to address all potential confounders at the design phase of a study. Therefore, it is necessary to consider confounding at the analysis phase of a study as well.