Hi,
I have the same problem too, especially when it comes to testing the main effect of groups.
I applied the same strategy by adding the smoothed grey matter images from time points 1 and 2 (T1+T2) for individual subjects and used one-way ANOVA between subjects for three group comparisons. I am able to create the design matrix without having any issues. But, I ran into a sphericity problem (please see the error below) when I tried running the model estimation using the spm.mat file.
Failed 'Model estimation'
Error using spm_est_non_sphericity (line 196)
Please check your data: There are no significant voxels.
Any valuable suggestions please?
thanks and regards,
Varun
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