Dear Bernhard,
> We want to analyze a PET study comparing two different groups (3
> patients=group1,and 3 healthy subjects=group2). For each group, three
> different conditions (A:rest, B:activity 1, C: activity 2) have been
> examined. There are 4 scans for each condition/subject. Now we want to
> calculate differences concerning overall activity (taking together
> condition B and C) against rest (condition A) between the two groups,
> i.e. analyse differences in activation/deactivation between patients
> and normals.{ ((B+C)-A)group1 against ((B+C)-A)group2} Can anyone tell
> us which is the appropriate study design setup in SPM 96b to do this
> and how the contrasts should be chosen.
Simply select multi-group with 2 groups. Each group has 3 [replicated]
conditions (and 0 covariates). For the particular group x condition
interaction you require the contrast weights would be (for conditions
A, B and C over both groups):
[-2 1 1 2 -1 -1] and its inverse.
I hope this helps - Karl
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