JoHo

A quasi-experiment differs from actual experiment in control. In a quasi-experiment researchers do not have full control over the conditions. Participants are not randomly assigned to the conditions. An example of a quasi-experiment:

Plastic surgery is done throughout the whole world. People who undergo this procedure state that their self-esteem and body image will get better after the procedure. But is that really the case? One way to find out is to randomly assign people to the plastic surgery or no-plastic surgery condition. This, of course, is not ethical, because you can not tell people to get plastic surgery just for your experiment. The researchers asked people who were already going to get plastic surgery to answer questions about their self-esteem. These people were measured on their measure of self-esteem before the surgery and 3, 6 and 12 months after the plastic surgery. The comparison group was a group of people who were also registered at the same clinic, but who had not undergone plastic surgery. They also answered questions about their self-esteem at the same time points as the first group. Participants have not been assigned randomly to a condition - so quasi-experiment.