Hi,
I've searched the archives and yet lack complete confidence that I am setting contrast and matrix files appropriately. Can someone please confirm the following that is specific to my study? ...
I have 2 groups and would like to control for age, gender, and handedness. If I want to know in which voxels FA is greater in patients than controls and vice versa, have I set the files up correctly?
EV1=Patients
EV2=Controls
EV3=age_demeaned (I subtracted the mean age of all subjects - both patients and controls - from each subject's age.)
EV4=gender_demeaned (I subtracted the mean gender of all subjects - both patients and controls - from each subject's gender.)
EV5=handedness_demeaned (I subtracted the mean handnessness of all subject - both patients and controls - from each subject's handedness.)
design.mat:
1 0 .21 -.31 .94
1 0 .22 .69 -.06
1 0 -.13 -.31 -.06
...
...
0 1 1.94 -.31 -.06
0 1 3.25 -.31 -.06
design.con:
1 -1 0 0 0
-1 1 0 0 0
command:
randomise -i all_FA_skeletonised -o outroot -m mean_FA_skeleton_mask -d design.mat -t design.con -n 5000 --T2 -V
A few more questions:
1) With this design, must I use -D (a simple yes or no will do)?
2) With this design, is it fair to say that the 3 covariates are being "controlled?" If not, what can be said about the covariates?
3) If I want to know in which voxels one of these covariates, say age_demeaned, correlates with each of the groups, what exactly should my contrast files look like? Like this?
1 0 1 0 0
1 0 1 0 0
4) If I want to know in which voxels age affects FA differently between the 2 groups, what exactly should my .con and .mat files look like? (If possible, can you please modify the above .mat and .con files for this question?)
Sorry for the necessary hand-holding, but I greatly appreciate your reply!
Amelia
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