Statistics Related to Within-Subjects Designs

If you decide to have students compute the dependent t test discussed in this chapter, assign pages 523-525 of Appendix E. In addition, you may want to help students with two important distinctions:
  • When to use the dependent t test versus when to use the independent groups t test; and

  • The standard deviation of the differences is different from the standard error of the differences.

    In discussing either one of these distinctions, you may find it helpful to use the "bag of tricks" example presented in

    Zerbolio, D. J. (1989). A "bag of tricks" for teaching about sampling distributions.

    Teaching of Psychology, 16, 207-209.

    If you decide to discuss within-subjects analysis of variance, consider

    1. Explaining how to decipher a within-subjects ANOVA table, and
    2. Showing students how to code data for a within-subjects design.

    If you want to go into additional depth in analyzing within-subjects designs, you could discuss

    1. Tukey's test of additivity, for violations of assumption of independence;

    2. nonparametric alternatives to ANOVA;

    3. planned comparisons;

    4. using MANOVA to analyze within subjects designs. The following reference is useful:

    O'Brien, R. G. & Kaiser, M. K. (1985). MANOVA method for analyzing repeated measures

    designs: An extensive primer. Psychological Bulletin,

    97, 316-333.

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