Quasi-Experiment in Psychology: Definition & Example

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  • 0:01 Definition of Quasi-Experiment
  • 1:04 Examples
  • 2:54 Advantages & Disadvantages
  • 3:58 Lesson Summary
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Lesson Transcript
Instructor: Chris Clause
In this lesson, you will learn to define the term 'quasi-experiment' and also learn why it is used in research. Following the completion of the lesson, you will have an opportunity to test your knowledge with a short quiz.

Definition of Quasi-Experiment

A quasi-experiment is designed a lot like a true experiment except that in the quasi-experimental design, the participants are not randomly assigned to experimental groups.

In a true experiment, research participants have an equal chance of being assigned to any condition of the independent variable (the one being manipulated by the researcher) that is involved in the study. So, for instance, if a researcher was examining the effects of caffeine on reading comprehension, she might randomly assign participants to one of three independent variable conditions: those who drink one cup of soda, two cups of soda, or no soda. She might then assess each person's reading comprehension abilities following exposure to the independent variable. In a true experiment, each participant who volunteered would have an equal chance of being assigned to any of the three groups.

Quasi-experiments are employed when the researcher is interested in independent variables that cannot be randomly assigned. Usually this happens when the independent variable in question is something that is an innate characteristic of the participants involved. Let's look at a couple of examples to help illustrate the point.


Here are two examples of simple quasi-experimental designs that will help you see the difference between a true experiment and a quasi-experiment.

Dr. Jones is a personality expert who studies the impact that personality traits have on intelligence. For the purposes of her current research project, she is interested in examining the IQ scores of people who score highly in each of the five 'Big Five' personality factors. Each of the five personality factors are a quasi-independent variable. Personality traits are inherent to each person, so random assignment cannot be used. Participants would initially be assigned to groups based on their personality assessment score across each of the five personality factors.

Now that Dr. Jones has her participant group assignments, she can examine the impact that personality factors may have on intelligence. If a true experimental design were used, each participant would be randomly assigned to each personality group regardless of whether or not they possessed those personality traits, which would not really address the question that Dr. Jones is asking.

Let's look at one more example. Dr. Loyd is a multicultural expert and is interested in the effect that race has on academic dishonesty. People cannot be randomly assigned to different race categories, so a quasi-experimental design is used.

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