Note: The Across Groups report appears only if you have specified an X, Grouping variable.
The Across Groups analysis corresponds to a simple repeated measures analysis. (You can get the same test results using the Manova personality of the Fit Model platform.)
Mean Difference
Shows the mean of the difference across rows in each group between the two paired columns. In other words, this is the within-subject by across-subject interaction, or split-plot by whole-plot interaction.
Mean Mean
Shows the mean of the mean across rows in each group across the two paired columns. In other words, this is the across-subject or whole-plot effect.
Test Across Groups
Two F tests determine whether the across-groups values are different:
Mean Difference
Tests that the change across the pair of responses is different in different groups.
Mean Mean
Tests that the average response for a subject is different in different groups