Confounding

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Step 4: Data Analysis Questions

3.	Explain how you would assess whether a potential confounder alters an effect estimate after adjusting for it in a multivariable model.
		a.	Look at the crude OR
		b.	Look at the adjusted ORs
		c.	Compare the crude OR to the adjusted OR

[ Follow this link to learn more about the evaluation of confounding.]
(Note: In the popup window, be sure to scroll down after each correct answer.)

4.	Would confounding due to socioeconomic status still be a problem if the investigators chose to conduct a cohort study instead of a case-control study?
		a.	Confounding would not be a problem in a cohort study
		b.	Confounding would still pose a problem in a cohort study
		c.	Confounding would be minimal in a cohort study compared to case-control study

5.	Stellman et al. matched controls to cases on four factors: age, sex, hospital, and hospital room. Other case-control studies match on fewer factors. Which technique is better and why?
		a.	The other studies are better because it is best to match controls to cases on as few factors as possible.
		b.	Stellman et al.’s study is better because it is best to match controls to cases on as many factors as possible.
		c.	It is not possible to determine which study would be better at controlling for confounding by looking at the number of matched factors.

6.	What if during data analysis investigators found that the use of vitamin supplementation was associated with artificial sweetener use and was an independent risk factor for bladder cancer. Should they attempt to control for this potential confounder?
		a.	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.
		b.	Yes, investigators should control for vitamin supplementation and describe the process of confounder selection in their Results section.
		c.	No, it is inappropriate to control for variables if they were not hypothesized as confounders a priori.

7.	Suppose investigators wanted to determine if confounding was present during the analysis stage of the study. What can be done at this stage to assess confounding?
		a.	Perform stratified analyses
		b.	Use restriction
		c.	Conduct matched analyses

8.	Shapiro, et al. matched controls to cases on two factors: age and geographic area, whereas Stellman and Wynder matched controls to cases on four factors: age, sex, hospital, and hospital room. Which study do you think is best at controlling confounding at the design phase of the study?
		a.	Shapiro et al's study is better because it is best to match controls to cases on fewer factors.
		b.	Stellman and Wynder's study is better because it is best to match controls to cases on more factors.
		c.	It is not possible to determine which study is better at controlling confounding by looking at the number of matched factors.

9.	Age was a potential confounder in this study. Choose an appropriate diagram representing the relationship of this potential confounder with exposure and outcome.
		a.
		b.
		c.

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?
		a.	Yes, investigators should still control for this confounder as they did for other confounding variables.
		b.	Yes, investigators should still control for this confounder and describe the process of confounder selection in the description of the results.
		c.	No, investigators should not control for any confounders which they did not specify a priori.

Learning
Objectives

>

Introduction
to Study

>

>

Design
Questions

>

Data
Analysis

>

Discussion
Questions