Quasi-Experimental Methods

A quasi-experiment is a research method in which the experimenter uses preexisting differences between participants rather than random assignment to allocate the participants to different conditions of the study. An example of a quasi-experiment is a comparison between the behavior of children at high risk and at low risk of autism spectrum disorder. The first condition corresponds to children who have an older brother or sister who has received a clinical diagnosis of an autism spectrum disorder from expert clinicians. The second condition corresponds to children who do not have an older brother or sister with autism spectrum disorder. For objective reasons, the researcher cannot assign the two conditions to all the participants.

Sometimes, researchers cannot randomly assign the participants to the experimental conditions for ethical ...