Dear SPM experts,
I have a 2 X 2 within-subjects factorial design, with factors A (two levels, A1 and A2) and B (two levels, B1 and B2). I am using a flexible factorial design in SPM12, with the following factors:
1. Subject
2. Factor A
3. Factor B
The settings of these factors are:
1. Subjects factor: independence - yes, variance - equal
2. A & B factors: independence - no, variance - equal
My first question, are the settings of these factors correct? Because I found here http://spm8.blogspot.de/2012/05/2-x-2-repeated-measures-anova.html , the author was setting the factor of A and B as: independence - no, variance – unequal.
As I understood from previous posts, I generate a design with following contrast:
Design (see attached "design"):
factor1: subject
factor2: A
factor3: B
Main effect: subject, A, B, 1, 2, 3
Interaction: A x B [2 3]
Contrasts
Main effect of A : 1 -1 0 0 0.5 0.5 -0.5 -0.5 Zeros (1,24)
Main effect of B : 0 0 1 -1 0.5 -0.5 0.5 -0.5 Zeros (1,24)
Interaction A x B : 0 0 0 0 1 -1 -1 1 Zeros(1,24)
Single regressor in main effect of A (e.g A1) : 1 0 0.5 0.5 0.5 0.5 0 0 ones(1,24)*[1/24]
Single regressor in main effect of B (e.g B1) : 0.5 0.5 1 0 0.5 0 0.5 0 ones(1,24)*[1/24]
single regressor in interaction A x B ( e.g. A2B1): 0 1 1 0 0 0 1 0 ones(1,24)*[1/24]
two single regressor in interaction A x B ( e.g. A1B2 and A2B2): 1 1 0 1 0 1 0 1 ones(1,24)*[2/24]
Could you check if these contrasts are correct?
Many thanks in advance,
Arkan
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