Thanks for suggestions, you are right, they are different analysis.
But they are the same data. Both A and B are above baseline. But when
I compare A and B, A and B become not above baseline? That what I
can't understand.
Xiang
On Mon, Jun 8, 2009 at 1:10 PM, Dasa Zeithamova
<[log in to unmask]> wrote:
> 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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