Robust Tests of Repeated Measures Means in Educational and Psychological Research

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Abstract
Numerous authors have maintained that when successive measurements are obtained from educational and psychological research, the traditional repeated measures F tests will not be valid (Danford, Hughes, and McNee, 1960; Humphreys, 1960; Jennings and Wood, 1976; McCall and Appelbaum, 1973; Wilson, 1967, 1974). The tests will be prone to too many false rejections because the data do not satisfy the validity assumption of circularity (Huynh and Feldt, 1970; Huynh and Mandeville, 1979; Rogan, Keselman, and Mendoza, 1979; Rouanet and Lepine, 1970). Multiple comparison tests that use a pooled estimate of error variance to obtain the standard error of the contrast of repeated measures means must also satisfy the circularity assumption to be valid. The purposes of this paper are to demonstrate that multiple comparison tests using a pooled error term are also dependent on the circularity assumption, and to show how to compute tests which are insensitive (robust) to this assumption.