Maxwell, Scott E.2011-02-112011-02-111980Maxwell, Scott E. (1980). Dependent variable reliability and determination of sample size. Applied Psychological Measurement, 4, 253-260. doi:10.1177/014662168000400211doi:10.1177/014662168000400211https://hdl.handle.net/11299/100094Arguments have recently been put forth that standard textbook procedures for determining the sample size necessary to achieve a certain level of power in a completely randomized design are incorrect when the dependent variable is fallible. In fact, however, there are several correct procedures-one of which is the standard textbook approach-because there are several ways of defining the magnitude of group differences. The standard formula is appropriate when group differences are defined relative to the within-group standard deviation of observed scores. Advantages and disadvantages of the various approaches are discussed.enArticle