To whom it may concern,
I am struggling in defining the contrast vectors for a 2x4 factorial design using the flexible factorial design in SPM.
So far I defined three factors: subject, group and condition. I have 2 groups and 4 conditions. I am interested in the main effect of group and condition and in the interaction of group x condition.
Thats what I found in the manual of Gläscher..... how to adapt that to the 2x4 factorial design (the example is a 2x3 factorial design).
Main Effects and Interaction:
1. Main effect: 2 (A)
2. Main effect: 3 (B)
3. Interaction: 2 3 (A — B)
Contrast Weights
1. Main effect of A: 1 -1 0 0 0 ones(1,3)/3 -ones(1,3)/3
2. Main effect of B: 0 0 -1 0 1 [-1 0 1]*[1/2] [-1 0 1]*[1/2]
3. Interaction A — B: 0 0 0 0 0 -1 0 1 1 0 -1
I am also interested in calculating t-contrasts in the meaning of post hoc tests (e.g., scans of group1_condition1 vs scans of group2_condition1). Is that also possible with the flexible factorial design?
Many thanks in advance.
Kind regards,
Catherine
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