True Experimental Design

The exact definition of true experimental designs has been debated. The term true experiment is sometimes used to refer to any randomized experiment. In other instances, the term true experiment is used to describe all studies with at least one independent variable that is experimentally manipulated and with at least one dependent or outcome variable. Furthermore, the word true has been interpreted to mean there are a limited number of correct experimental methods. Regardless of the exact definition, the distinguishing feature of true experimental designs is that the units of study—be they individuals, animals, time periods, areas, clinics, or institutions (i.e., whoever or whatever is assigned to an experimental condition is the unit)—are randomly assigned to different treatment conditions.

Because of the various meanings and the ...