Within-subjects designs: To use or not to use?

Anthony G. Greenwald
1976 Psychological bulletin  
This article considers the several factors pertinent to deciding whether a within-or between-subjects design should be employed for a research application. A general principle favoring within-subjects designs is the statistical efficiency afforded by removing subject variance from error terms used to test treatment effects. Within-subjects designs, however, are often faulted for being subject to context effects of practice, sensitization, and carry-over that may limit interpretation of results.
more » ... At the same time, between-subjects designs are not devoid of context effects, but rather have #the context that a single treatment affords itself. Since ecological validity of results depends on the correspondence of the research context to the generalization context, within-subjects designs may he preferred when the generalization context includes the equivalent of several concurrent treatments. The discussion focuses additionally on (a) procedures 'to minimize practice, sensitization and carry-over effects in within-subjects designs when t h e y a;e these effects to advantage in research. not desired, and (b) means of using
doi:10.1037/0033-2909.83.2.314 fatcat:p4lclhb2onfq3f37jhhvziufi4