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We have already alluded to sources of error in epidemiologic studies, and you have learned a number of methods for evaluating random error. We will now turn our attention to biases, i.e., systematic errors that are usually unwittingly introduced into a study by the investigators or the subjects that cause an over- or under-estimate of an association between an exposure and a health outcome.

In this module we will focus on selection bias and information bias.

By identifying common mechanisms of bias, we can design studies to limit these pitfalls, predict the impact of bias on our study results, and critically evaluate the published literature.

Essential Questions:

  1. What systematic errors in population health research can lead to incorrect conclusions?
  2. Why do these errors occur? Are they specific to certain study designs?
  3. What is selection bias and information bias?
  4. How can we estimate the effect of bias on my findings? How can we avoid or minimize these errors?

Learning Objectives

After completing this module, you will be able to: