Dear all,
I would like to correlate a behavioral measure with FA values on tbss
skeleton. I wanted to do it for 2 subgroups of my sample separately, but
I am not able to split the all_FA_skeletonized file (here I am referring to
my email "Fslroi on all_FA_skeletonised - output does not match the input").
In case you have an idea how to overcome the problem, I will be very
grateful.
In meantime I wanted to run some analyses with a design matrix for all
subjects together.
Here are some of my designs and I wanted to ask if they make sense the way i
describe them (I read previous posts but I am still not sure what is the
best to answer my questions). Unfortunately I have no experience with FEAT
design matrices, hence these basic questions.
As I mentioned before, I have 2 subgroups (younger and older), in designs
below first 3 entries belong to 1 group, the remaining 3 to the other.
1) How BEH correlates with FA in the whole sample?
Group EV1(beh, demeaned values)
1 -1
1 -3
1 -5
1 3
1 1
1 5
Contrast : -1 (I expect negative correlation)
Randomise with -D option
Or if the two subgroups have different means for BEH, should I split EV1
into two Evs:
EV1 Ev2
-1 0
-3 0
-5 0
0 3
0 1
0 5
And then skip -D?
2) How BEH correlates with FA after regressing out for age?
Group EV1(beh, demeaned values) EV2 (AGE, demeaned)
1 -1 -12
1 -3 -10
1 -5 -7
1 3 12
1 1 7
1 5 10
contrasts: -1 0
Randomise with -D (as there is no EV that models the mean)
Or would it make more sense to orthogonalize EV1 with respect to EV2 by
clicking it in Glm_gui? (if I know that BEH and age are not highly
correlated?)
3) How FA correlates with BEH, after regressing out for agegroup to which a
subject belongs?
Group EV1 (young) EV2 (old) EV1(beh, demeaned values)
1 1 0 -1
1 1 0 -3
1 1 0 -5
2 0 1 3
2 0 1 1
2 0 1 5
Contrasts 0 0 -1
1 -1 0 (where younger have higher FA than older, after regressing out for
BEH?)
Having EV1 and EV2 that model the mean, I dont need to add -D option. Is it
correct?
4)
Group EV1(age, demeaned values) EV2 (BEH young, demeaned) EV3(BEH old)
1 -1 -12 0
1 -3 -10 0
1 -5 -7 0
1 3 0 12
1 1 0 7
1 5 0 10
Contrast 0 1 -1 (would it tell me where BEH correlates with FA higher in
young than old adults, after regressing out for age?)
5) or would it be more meaningful to make an interaction analysis (Beh and
age interaction) using F-tests? If yes, how should it look like?
Thank you very much for help in advance,
Best,
Aga
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