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Hello experts,
I am interested in identifying regions of interest by comparing cortical volume (CV) between controls and patients.
After including age and sex as my covariates, I identified regions X1 and X2, which showed significantly lower CV for patients (as compared to controls).
But after I include ICV as another covariate, my results show that for none of the areas there is any significant difference in CV, i.e. my results vanish.
When I checked subjectwise ICV for each group, I found that there is almost significant difference (two-sampled t-test, p = 0.067) in ICV between two groups, but interestingly mean group ICV for patients group was larger compared than mean ICV for controls. But as I said earlier, regions X1 and X2 had significantly lower CV for patients (as compared to controls), when I didn't include ICV as covariate.
Could you please help me in interpreting these results? Is there any advice regarding inclusion of ICV as covariate? Or my results are purely because of differences in ICV between groups, and there is no real findings regarding the regions identified (X1 and X2)?
Thanks a lot !