Workspace Node: GLM Custom Design - Results - Post-hoc Tab

In the GLM Custom Design node dialog box, under the Results heading, select the Post-hoc tab to access options to perform post-hoc comparisons between the means in the design. A discussion of the rationale and applications of planned comparisons along with post-hoc tests is also provided in the Contrast Analysis and Post-Hoc Tests. Note that these options are only available if the current design contains effects for categorical predictor variables or within (repeated measures) effect. For a general description of post hoc comparisons and additional information on post-hoc tests involving random effects and repeated measures, see Post-hoc Tests in GLM, GRM, and ANOVA.

Element Name Description
Effect Select the desired effect in this drop-down box. Post-hoc comparisons are performed on the marginal means (weighted observed) for effects involving only categorical predictor variables.
Dependent variables Click this button to display a variable selection dialog box, where you select the dependent variables for which to compute the post hoc tests; a results spreadsheet will be created for each dependent variable that is selected.
Display The options in this group box control the manner in which the results for the requested post hoc tests will be displayed. For detailed descriptions of the Significant differences, Homogeneous groups, Confidence intervals, and Critical ranges options, see Display Post-hoc Tests Results in GLM, GRM, and ANOVA.
Error term In this group box, select an error term (estimate of the error variance sigma) for the post hoc comparisons. For detailed descriptions of the Between error, Within error, Between; within; pooled, and MS, df options, see Error Term for Post-hoc Tests in GLM, GRM, and ANOVA.
Fisher LSD Select this check box to produce a spreadsheet containing the results of the Fisher LSD test. This test is equivalent to the t-test for independent or dependent samples (see also Basic Statistics and Tables), based on the N in the respective cells of the design involved in the comparison. It offers the least amount of protection against the increased alpha error rate due to multiple post-hoc comparisons. The results will be displayed in the format specified in the Display group box (see above).
Bonferroni Select this check box to produce a spreadsheet containing the results of the Bonferroni test. The Bonferroni procedure involves tests of multiple a priori hypotheses while controlling the experimenter-wise error rate; specifically, it can be shown that the type 1 error rate (alpha(exp)) for a set of comparisons will not exceed the sum of the error levels (alpha(ind)) for a set of m tests of significance; or alpha(exp) < m*alpha(ind). The Bonferroni procedure uses this inequality to adjust the significance levels for the individual post-hoc comparisons. The results will be displayed in the format specified in the Display group box (see above).
Scheffé Select this check box to produce a spreadsheet with the post-hoc p-values for the Scheffé test. The Scheffé test is usually more conservative than the Newman-Keuls or Duncan's test (see Winer, 1962). The results will be displayed in the format specified in the Display group box (see above).
Tukey HSD Select this check box to produce a spreadsheet containing the results of the Tukey HSD test. The Tukey HSD test falls between the Newman-Keuls (see below) and Scheffé (see above) procedures with regard to conservatism. The results will be displayed in the format specified in the Display group box (see above).
Unequal N HSD Select this check box to produce a spreadsheet containing the results of the Tukey Unequal N HSD test. This test is a generalization of Tukey's test to the case of unequal samples sizes (see Spjotvoll & Stoline, 1973, p. 975). The results will be displayed in the format specified in the Display group box (see above).
Range tests (multi-stage tests) The post-hoc tests contained in this group box test the significance of ranges, given the respective number of samples. The results will be displayed in the format specified in the Display group box (see above).
Newman-Keuls Select this check box to produce a spreadsheet containing the results of the Newman-Keuls test. This test is based on the studentized range statistic. Computationally, Statistica first sorts the means into ascending order. For each pair of means, Statistica then assesses the probability under the null hypothesis (no differences between means in the population) of obtaining differences between means of this (or greater) magnitude, given the respective number of samples. Thus, it actually tests the significance of ranges, given the respective number of samples. Note that Statistica does not merely report cut-off values for p, but will compute the actual probabilities based on the distribution of the studentized range statistics.
Crit. ranges Select this check box to produce a spreadsheet containing the critical ranges for the Newman-Keuls test. This button is only active if you have selected Critical ranges in the Display group box (see above).
Duncan's Select this check box to produce a spreadsheet containing the results of Duncan's test. This test is based on the same logic as the Newman-Keuls procedure (see above); however, it uses a less conservative test criterion (see, for example, Milliken & Johnson, 1984).
Crit. ranges Select this check box to produce a spreadsheet containing the critical ranges for Duncan's test. This button is only active if you have selected Critical ranges in the Display group box (see above).

Comparisons with a Control Group (CG). Use the options in this group box to perform Dunnett's test.

Dunnett Select this check box to produce a spreadsheet containing the results of Dunnett's test. This procedure can be used to compare a set of k-1 treatment groups against a control group (see Dunnett, 1955). Note that the computations involved in the estimation of the p-values for the Dunnett test can be very time consuming, so large problems (many comparisons) may take some time to complete.
< CG Select this option button to indicate that the post-hoc comparisons (and associated p-values) should be one-sided (mean x(i) < x(control)).
> CG Select this option button to indicate that the post-hoc comparisons (and associated p-values) should be one-sided (mean x(i) > x(control).
<>CG Select this option button to indicate that the post-hoc comparisons (and associated p-values) should be two-sided (x(i) ¹ x(control)).
CG cell # Enter the number of the cell (treatment group) to be used as the control group in the comparison in the CG cell # field. Refer to the spreadsheet of means (e.g., see the Means tab) for the numbers of cells in the current Effect.

Options / C / W. See Common Options.

OK Click the OK button to accept all the specifications made in the dialog box and to close it. The analysis results will be placed in the Reporting Documents node after running (updating) the project.