Greenwald, A. G. (1976). Within-subjects designs: To use or not to use? Psychological Bulletin, 83(2), 314-320.
http://dx.doi.org/10.1037/0033-2909.83.2.314
Examines several factors pertinent to deciding whether a within- or between-Ss design should be employed for a research application. A general principle favoring within-Ss designs is the statistical efficiency afforded by removing S variance from error terms used to test treatment effects. Within-Ss designs, however, are often faulted for being subject to context effects of practice, sensitization, and carry-over that may limit interpretation of results. At the same time, between-Ss 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-Ss designs may be preferred when the generalization context includes the equivalent of several concurrent treatments. Procedures to minimize practice, sensitization and carry-over effects in within-Ss designs when they are not desired, and means of using these effects to advantage in research are discussed. (PsycINFO Database Record (c) 2016 APA, all rights reserved)