Wu, Xiaoying wrote:
> Dear Dr. Penny and experts,
>
>
>
> Question about paired t-test and 2nd level analysis. I have two groups
> patients, each has 32 subjects, each subject has 2 scan (two time
> points). I had performed paired t-test on these two groups separately
> and have the results between two time points for the two group separately.
>
>
>
> My question is how to find out these changes are different or not
> between these two groups?
>
> One possible solution might be: generate contrast image for each subject
> and perform two sample t-test on these con*.imgs (as a 2nd level
> analysis).
For each subject create the contrast image 'time2 - time1'.
Do this for both patient groups.
Then, as you say, all you need to do is a two sample t-test.
A [1 -1] F-contrast will show the main effect of group ie. any voxels
where the (time) differential effect is different between groups.
Best,
Will.
> If this is the correct way to do it, how to generate these
> contrast images for each subject in spm2? Or if not, how to conduct the
> test correctly?
>
>
>
> Thank you for any suggestion,
>
>
>
> Xiaoying
>
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--
William D. Penny
Wellcome Department of Imaging Neuroscience
University College London
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London WC1N 3BG
Tel: 020 7833 7478
FAX: 020 7813 1420
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URL: http://www.fil.ion.ucl.ac.uk/~wpenny/
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