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I see a t test as a test of whether you have enough subjects to show a difference ("because the probability of an effect being zero is vanishingly small, given enough scans or subjects one can always demonstrate a significant effect at every voxel" KJF).  With only 16 mice, you won't have a particularly powerful VBM analysis.

Best regards,
-John


On 23 June 2015 at 16:17, Ned <[log in to unmask]> wrote:

 

Hello SPM VBM experts

I tried to compare the differences between two mouse groups ( control vs knockout), I was able to do registration, normalization and segmentation nicely. I did 0.5 mm isotropic smoothing  Then I did 2 sample t test on grey matter with p=0.01 with 200 clusters, I got the above results. I am wondering that why I am getting few clusters with significant voxels? Does this look normal? Please share your suggestions.

Thanks

Ned