ABSTRACT
A common question, frequently faced by researchers, concerns the use of a between- or within-subjects experimental design. In the between design each subject is exposed to a single treatment, whereas in the within (or repeated measures) design, subjects are exposed to several or all the treatments that are included in the study. Faced with the choice of manipulating the independent variable in a between- or within-subjects design, which one should the investigator use? The purpose of this chapter is to discuss the considerations that should guide researchers in making their choice.
