Perhaps I misread your question, but If I understand it correctly, you
are doing two VERY different analyses in Situation 1 and Situation 2, so
you shouldn't be surprised that the results are different.
In 1, you look which areas are active in cond A, and which are active in
B. You get areas where A> baseline, and areas where A>baseline. In 2,
you are essentially performing a t-test looking for areas where A>B
(i.e. where A-B>0). Neither of A or B has to be above baseline for A>B
and both A & B can be above baseline and equal.
Is that what you were after?
Dasa
Xiang Wu wrote:
> Hi all
>
> Given two conditions A and B.
>
> In situation 1, I perform group analysis one sample t-test on A and B
> "separately". So I got activations for A and B.
>
> In situation 2, I put A and B in "one group analysis". I conduct two sample
> t-test, paired t-test, or full-factorial (one factor, two level), the
> results were similar. However, The activations for A and B in "one group
> analysis" are largely different from those by "separate" one sample t-test,
> not only the significance level, even the activation patterns look different.
>
> I really confused. Can somebody explain the reason for me? I think there is
> no problem to get activation of each condition with one sample t-test, but I
> have no idea what happened when put multiple conditions in one group analysis.
>
> Thanks
> Xiang
>
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