Hi
I am trying to get my head around setting up 2nd level stats in FSL. I have
2 subject groups. Each subject performs an nback working memory task under 3
conditions. I've analyzed all my subjects at the first level and made 3
copes, 1 for each task condition.
At the second level would I select the COPE images or the feat directories?
I think it would have to be the cope images. I tried selecting the FEAT
directories but the events don't seem correct then.
Anyway, assuming that I select the copes I selected them in the order
subj1-cope1, subj1-cope2, subj1-cope3, subj2-cope1 and so on.
Here is what I think the model would be
grp ev1 ev2 ev3 ev4 ev5 ev6 ev7 ev8 ev9 ev10
subj1a-cope1 1 1 0 0 0 0 0 1 0 0 0
subj1a-cope2 1 0 0 1 0 0 0 1 0 0 0
subj1a-cope3 1 0 0 0 0 1 0 1 0 0 0
subj2a-cope1 1 1 0 0 0 0 0 0 1 0 0
subj2a-cope2 1 0 0 1 0 0 0 0 1 0 0
subj2a-cope3 1 0 0 0 0 1 0 0 1 0 0
subj3b-cope1 2 0 1 0 0 0 0 0 0 1 0
subj3b-cope2 2 0 0 0 1 0 0 0 0 1 0
subj3b-cope3 2 0 0 0 0 0 1 0 0 1 0
subj4b-cope1 2 0 1 0 0 0 0 0 0 0 1
subj4b-cope2 2 0 0 0 1 0 0 0 0 0 1
subj4b-cope3 2 0 0 0 0 0 1 0 0 0 1
ev1 = group a cond 1
ev2 = group b cond 1
ev3 = group a cond 2
ev4 = group b cond 2
ev5 = group a cond 3
ev6 = group b cond 3
ev7-ev10 subject effects
Do I need to have a mean column in this analysis?
Now for the contrasts, which is where I get very confused
Main effect of group (F-test)
ev 1 2 3 4 5 6 7 8 9 10 F
1 0 1 0 1 0 0 0 0 0 on
0 1 0 1 0 1 0 0 0 0 on
Main effect of working memory (I think I only have to test 2/3 contrasts for
this?) (F-test)
ev 1 2 3 4 5 6 7 8 9 10 F
1-2 1 1 -1 -1 0 0 0 0 0 0 on
2-3 0 0 1 1 -1 -1 0 0 0 0 on
Interaction of group with working memory (I think I only have to test 2/3
contrasts for this?) (F-test)
ev 1 2 3 4 5 6 7 8 9 10 F
a1-2 1 0 -1 0 0 0 0 0 0 0 on off
b2-1 0 -1 0 -1 0 0 0 0 0 0 on off
a2-3 0 0 1 0 -1 0 0 0 0 0 off on
b3-2 0 0 0 -1 0 1 0 0 0 0 off on
What if I wanted to look at a simple t test of group differences for cond 1
-3 would that be the following
ev 1 2 3 4 5 6 7 8 9 10
(a1-a3)-(b1-b3) 1 -1 0 0 -1 1 0 0 0 0
How would I get the overall standard anova result?
thanks,
Darren
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