Hi there,
I'm running an fMRI analysis and I'm trying to set up a design matrix to perform an ANOVA with 3 groups of subjects (controls, two groups of patients) and one covariate (task performance).
I set up the design matrix like in the example below:
Group EV1 EV2 EV3 EV4
1 1 0 0 9,70
1 1 0 0 9,70
1 1 0 0 9,70
1 1 0 0 9,70
1 0 1 0 7,70
1 0 1 0 4,14
1 0 1 0 -12,52
1 0 0 1 -10,30
1 0 0 1 -20,86
1 0 0 1 -6,97
CONTRASTS:
1 -1 0 0
1 0 -1 0
0 1 -1 0
-1 1 0 0
-1 0 1 0
0 -1 1 0
Is this correct? Is it the same if I specify the value 1,2,3 for the column "Group" and split the performance column (EV4) in 2 different columns like below (demeaning for each column separately and deleting the column of the controls'performances, since it woul be all 0)?
Group EV1 EV2 EV3 EV4 EV5
1 1 0 0 0 0
1 1 0 0 0 0
1 1 0 0 0 0
1 1 0 0 0 0
2 0 1 0 7,3 0
2 0 1 0 3,75 0
2 0 1 0 -12,9 0
3 0 0 1 0 2.41
3 0 0 1 0 -8.15
3 0 0 1 0 5.74
What is the difference between the two designs, and which is better?
Thank you in advance for your help.
Giulia
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