Association and Bias in Observational Studies


This week you will review different types of bias, present an example of a study, and discuss whether bias was a factor in the study outcome. You will also discuss how the study design could have been altered to minimize or eliminate the risk of invalidating the results.

To prepare for this Discussion:
• Review the types of bias listed below.
o Non-differential recall bias
o Differential recall bias
o Publication bias
o Loss to follow-up
o Refusal to participate
o Interviewer bias
o Confounding
Select one type of bias from the list above, and consider the ways that bias could impact a study.

To complete this Discussion, post a real or hypothetical example of one study by Day 4. You can use one of the studies you designed during Weeks 3 or 4 or search for a different study.

• How could bias be introduced in the study?

• Would the bias be considered a selection bias or an information bias? Why?

• Name two or three variables that might be possible confounders in your study.

• Describe at least one method of controlling those confounding variables.
Hills Criteria of Causation

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