Hi Guillaume,
As per your previous suggestion, I tried doing a paired t-test for the three groups separately. Then, three contrast images were created, one for each group to apply ANOVA between groups. Subsequently, there was an error prompting 'spm_est_non_sphericity', when I ran the model estimation.
Alternatively, I applied imcal function to compute the differences in time points 1 and 2 within-subjects and and then incorporated the data into ANOVA for three group differences. Again, it prompted with the same error 'spm_est_non_sphericity', when I ran the model estimation.
I am not sure what does this mean exactly? is there a solution to resolve this issue?
thanks,
kind regards,
Varun
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