Multiple comparisons 1. Multiple comparisons The example The null hypothesis Variance estimates or mean squares The F ratio Decision rules and statistical significance Decision errors Selecting the most appropriate multiple comparison test Selecting a multiple comparison test and Type I errors Definitions and meanings of Type I errors in multiple comparison tests Types of multiple comparisons Test statistics 2. Priori comparisons Orthogonal comparisons Characteristics of orthogonal comparisons Decision rule for evaluating orthogonal comparisons Strategies for developing sets of orthogonal comparisons Protection levels for orthogonal comparisons Orthogonal polynomials Nonorthogonal comparisons Summary and recommendations 3. Post hoc comparisons: pairwise methods Rationale for range tests Sampling distribution of ranges Tukeys honestly significant difference test (HSD) Newman Keuls test Tukeys wholly significant difference test (WSD) The Duncan Test Lease significant difference test (LSD) Pairwise comparisons and Type I error Comparisons of pairwise methods Dunnetts test 4. Post Hoc comparisons: The Scheff(c)♭ Test Controls for reducing Type I errors in post hoc comparisons Conducting the Scheff(c)♭ test Characteristics of the Scheff(c)♭ test 5. Multiple comparisons in factorial designs Familywise Type I error A nonquantitative approach for examining interactions Simple Main effects Multiple comparisons on interactions Range tests and interactions Planned comparisons and interaction effects 6. Additional considerations Unequal sample sizes Violations of assumptions Concluding remarks