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Keywords:

  • Repeated measures designs;
  • Sphericity assumption;
  • Multivariate analysis of variance;
  • False positives

ABSTRACT

Violation of the validity assumptions of repeated measures analysis of variance continues to be a problem in psychophysiology. Such violation results in positive bias for those tests involving the repeated measures factor(s), Recently it has been shown that the tests of simple interactions and multiple comparisons are even more vulnerable to bias (Boik. 1981; Mitzel & Games, 1981). The present paper offers a discussion of the validity assumptions for both overall and sub-effect tests and describes a multivariate approach which allows exact analysis of such designs. A modification of the univariate approach is also described. Validity concerns for both approaches are much less problematic than those of the traditional approach.