There are four types of validity discussed in your book. The focus of chapter 3 is on internal validity, which is basicaly getting at how confident we are that the results of our study came from our independent variable (i.e., results are caused by our IV and not some outside confounding variable).

In this discussion, describe potential confounds to internal validity described in the chapter as if you are describing them to an family member or friend. Bring in examples from the literature and popular press as part of your description.

This topic is very important in designing your study. Thus, you will really want to understand it well. Feel free to use this discussion to ask questions.