Читать книгу Introduction to Abnormal Child and Adolescent Psychology - Robert Weis - Страница 135

Experiments allow us to infer causal relationships between variables because participants are randomly assigned. Sometimes, however, researchers are not able to conduct true experiments because random assignment is not possible. Instead, researchers conduct quasi-experiments. In a quasi-experimental study, researchers manipulate an independent variable (e.g., provide treatment) and note changes in a dependent variable (e.g., children’s outcome). However, they do not randomly assign participants to different groups, so they cannot infer that the treatment caused those outcomes. The term “quasi” means “looks like.” A quasi-experimental study looks like a true experiment, but it lacks an experiment’s essential ingredient: random assignment.

Let’s look at three of the most common types of quasi-experimental studies used in the field of abnormal child psychology: pretest-posttest studies, nonequivalent groups studies, and single case studies.