Dear SPM experts,
I have a problem with the analysis of a 'double contrast' like (A>B) >
(C>D). I did this on second level with a paired t-test after creating
the difference maps in the contrast manager.
Now I want to do two things with this double contrast, but I couldn't
find any solution for it. First, I would like to create a correlation
map with a behavioural covariate. I know that in a paired t-test,
there is the option to include a covariate, but you need to input 2
values per subject. If I do this - how do I interprete the resulting
correlation map for that covariate? It is the activity ACROSS (A>B)
and (C>D) that correlates with the covariate, right? But what I am
looking for is the correlation of the double contrast with a
difference between the 2 values of the covariate. Is there any way to
do that? Can I somehow create a double contrast in a simple t-test?
And second, I would like to compare the double contrast with the same
double contrast of another group.
I hope, someone can help me, I'm really stuck with this problem. I'd
appreciate any answers. Thank you!
Julian
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