Hi Tiffany
> I am new to SPM and have a question about the paired-t-test in the 2nd
> level. I wanted to compare two con images from the same subject, so I
> entered con_0001.img and con_0002.img as a pair in the paired-t-test.
> However, all of the betas (below the design matrix) are gray, indicating
> that none of them is uniquely specified. Attached is a picture of it. I do
> not have this problem when I was building a design matrix for each subject
> in the 1st level. Is it saying that I can't do a paired-t-test for con_0001
> and con_0002? I also tried different pairs for the same subject but I got
> the same thing, i.e. gray betas.
The 2nd level tests are designed for group analysis; if you just want
to compare two contrasts in a single subject, you should do this
within a 1st-level design matrix. If that's not clear, then feel free
to reply with an example of your design and design matrix. :)
Hope this helps,
Jonathan
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