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Quizzes

Quiz 10, Module Confounding

10. Suppose that during data analysis, investigators found that the number of abortions performed was associated with estrogen use and was an independent risk factor for endometrial cancer. Should they attempt to control for this confounder?

  1. Yes, investigators should still control for this confounder as they did for other confounding variables.
  2. Yes, investigators should still control for this confounder and describe the process of confounder selection in the description of the results.
  3. No, investigators should not control for any confounders which they did not specify a priori.
Answer (a) — incorrect: Since attempts to minimize confounding can only be made for known confounders, it is necessary to look for confounders during the analyses as well. However, it is also important to report the process of selection of confounding variables in the description of results (i.e., a priori confounders vs confounders which were identified in the data analysis step).
Answer (b) — correct: It is important to report the process of selection of confounding variables in the description of results (i.e., a priori confounders vs confouders which were identified in the data analysis step). The information on the process of adjustment for confounders is usually placed in the Methods section for published articles.
Answer (c) — incorrect: It is not always possible to know all the potential confounders at the beginning of the study. This may happen when investigating an exposure-- disease association which has not been studied well or if cost and feasibility may 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.