Hi Greg,


It depends on how you defined your second-level covariates, but assuming that you used two dummy-coded covariates, one for group1 subjects, and another for group2 subjects, you should then select both of these covariates in the 'between-subject effects' list, and also both of your conditions ('pre' and 'post') in your 'between-condition effects' list, and then enter the following contrast values:

1) main effect of group
   Between-subject contrast: [-1 1]
   Between-condition contrast: [.5 .5]

2) main effect of condition
Between-subject contrast: [.5 .5]
Between-condition contrast: [-1 1]

3) interaction between group and condition
Between-subject contrast: [-1 1]
Between-condition contrast: [-1 1]

Other additional contrasts of interest may be:

4) F-test for group effects across any of the two conditions
Between-subject contrast: [-1 1]
Between-condition contrast: [1 0; 0 1]

5) F-test for condition effects across any of the two subject groups
Between-subject contrast: [1 0; 0 1]
Between-condition contrast: [-1 1]

Hope this helps
Alfonso
Originally posted by Greg Book: