One of the most important aspects of all research is how we control the factors that can threaten the validity of our conclusions. There are two ways that we use the word control in psychological research. The first is as a standard for comparison. If our experimental groups differ on only one IV, then we conclude that any observed differences between the groups following the experimental manipulation are a result of our manipulation of the IV. All other competing explanations are ruled out by the existence of the control group(s) or control condition(s). The second meaning of control is as an attempt to constrain or eliminate competing sources of variability in our experiment.

Why Is This Important?
When we do research, we want it to have a good, valid result. Paying attention to all of those factors that can introduce bias or error into our studies will help us design a better study.

We can use general strategies to achieve control in our studies, we can apply strategies specific to our study design, and we can use replication as a control. Let's begin with general strategies.