Dear Dr Doug,
I have two groups of subjects (80 patients and 40 controls). I analyzed the
data using Freesurfer v6.0.
I want to study the difference between the groups in "precentral gyrus volume".
After "recon-all" I built Qdec table and I used Qdec to compute the comparison
by including eTIV a covariate. After correcting the results using Monte Carlo
simulation or adjusting for FDR I found no difference between the groups in
volume neither in surface area.
I adjusted the precentral gyrus volume values for eTIV using the commands:
mri_label_volume -eTIV $SUBJECTS_DIR/${i}/mri/transforms/talairach.xfm 1948
$SUBJECTS_DIR/${i}/mri/wmparc.mgz 2017
mri_label_volume -eTIV $SUBJECTS_DIR/${i}/mri/transforms/talairach.xfm 1948
$SUBJECTS_DIR/${i}/mri/wmparc.mgz 2024
I extracted the adjusted volume values to SPSS then I ran box plots comparison
between the groups and I found difference at (P<0.0001)
Why Qdec doesn't show the difference between the groups although the p value is
very small. What I am doing wrong in Qdec? Is it wrong to include eTIV a
covariate?
Thank you for any advice
John_______________________________________________
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