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What do you do in a Repeated-Measures ANOVA

The condition of sphericity (denoted as ?) for within subj designs

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What do you do in a Repeated-Measures ANOVA

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    1. Chapter_11 Repeated-Measures Design (GLM 4)?

    2. What do you do in a Repeated-Measures ANOVA? Testing the same subjects in different conditions Extension of the related, within-subjects design t-test? Expl.: You measure with a questionnaire the enjoyment of a party after no alcohol, 1 pint, 2 pints, 3 pints, 4 pints Advantage: As with the related t-test, the unsystematic variance is reduced, since we are testing the same subjects New assumption: sphericity

    3. The condition of sphericity (denoted as ?) for within subj designs – also called circularity Between subj design When analysing data from different participants, you have to assume homogeneity of variances, i.e., same variances in all groups Homogeneity of variances is tested with Levene's test Within subj design Since your subjects are always the same, there will necessarily be a relation between the measurements in the various conditions in a within subj design. While the relations cannot be independent they should be the same between all pairs.

    4. Compound symmetry and sphericity (?? Sphericity is a special case of a more general condition of compound symmetry. Compound symmetry means that (a) Both the variances across conditions are equal (like homogeneity of variances) and (b) The covariances between all conditions are equal Sphericity is a less restricted form of (b). It requires that the differences between pairs of treatment levels (the conditions) have similar variances. ? For each pair of treatment levels, the differences between each pair of scores should have the same variance.

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