We cannot interpret the findings of an experiment unless we know whether the experimental manipulation "worked". A manipulation check is something we build into the study design to tell us how well we did. Most manipulation checks are incorporated directly into the study design. Others are included at the end of the study in the debriefing. The nature of the manipulation check varies by type of research. A manipulation check for a laboratory experiment may look very different from the manipulation check for a clinical trial. Let's consider some possibilities for both types of experiments.

Why Is This Important?

Good experiments require a thoughtful, and sometimes clever, experimental manipulation. In order to draw valid conclusions about an experiment, this manipulation has to work. The manipulation check is what tells us whether the experimental manipulation worked or not.