hi
> Dear all:
>
> If I had a five conditions fMRI experiment, and made the following two
> t-contrasts using spm2 :
>
> [1 1 1 1 -1] and [1 0 0 0 -1;
>
> 0 1 0 0 -1;
>
> 0 0 1 0 -1;
>
> 0 0 0 1 -1]
>
> Are they all valid? And are they the same? If not, what are they
> meaning separately?
>
> Tank you very much!
>
well, they are not all valid and they are not the same ..
1. When you enter a contrast, the sum of coef must be 0 and thus [1 1 1
1 -1] is invalid (you can try but SPM contrast manager will refuse to do
that) .. if you want to oppose one condition against the others the
correct contrast would be [1 1 1 1 -4]
2. in the second case you test if any of these contrasts (or
combinations) is significant .. but those ones are correct as they all
sum up to 0
best
cyril
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