Pretest-Posttest Design: Definition & Example

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  • 0:07 Definition
  • 1:38 Example 1
  • 4:00 Example 2
  • 5:35 Lesson Summary
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Lesson Transcript
Instructor: Devin Kowalczyk

Devin has taught psychology and has a master's degree in clinical forensic psychology. He is working on his PhD.

This lesson explores the process and technique of using a pretest-posttest design in psychology. Two simple examples will allow you to understand how to apply this type of design in a future experiment.


You've probably got some ideas of how experiments should be run. Why don't researchers just look at something, poke it with a stick, and then study the changes? Researchers are always making things super complicated.

I am glad to inform you that there is a methodology very similar to this, most of the time occurring without the stick. A pretest-posttest design is usually a quasi-experiment where participants are studied before and after the experimental manipulation. Remember, quasi-experimental simply means participants are not randomly assigned. It is possible to have a control group, or a group who doesn't receive the manipulation, but we will not be looking at that in this lesson. In a pretest-posttest design, there is only one group and all of them are in the experimental condition.

The reason you run a pretest-posttest experiment is to see if your manipulation, the thing you're looking at, has caused a change in the participants. Since everyone is being manipulated in the same way, any changes you see across the group of participants is likely from the manipulation. This means you test them before doing the experiment, then you run your experimental manipulation, and then you test them again to see if there are any changes. So how does this really work?

Example 1

Have you ever tried to go about your day when you haven't showered, brushed your teeth, or really cleaned yourself? Let's say you're a researcher who is interested in how much the feeling of being unclean affects judgment and general knowledge. You settle on a pretest-posttest design. You will administer a pretest on general knowledge and judgment, then have your experimental manipulation of the participants not cleaning themselves, then perform a posttest using the same or similar tests.

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