your results could have vanished after ICV correction for one of two
reasons: the CV difference became less or the values became noisier (or
a combination). So check in your data which one of those things happened.
On 7/23/18 8:30 PM, Martin Juneja wrote:
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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 !
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