ABSTRACT
In this chapter, we want to reconsider the various threats to internal validity we introduced in chapter 8. What can a researcher do about them? Can they ever be eliminated? If not, can they at least be controlled to some degree? Later on in the chapter, we describe some of the ways by which many of these threats can be controlled, and also illustrate how the researchers tried to control for them in the two studies analyzed in chapter 8. First, however, we discuss the experiment—an extremely powerful means of controlling such threats.
