Dear Freesurfers,
I used Qdec to do two-group comparison on cortical thickness. Demeaned age was used as the covariate. The question I¹m looking at is that ³Does the thickness-age correlation differ between C1 and C3?²
When FWHM=15mm was chosen, I got confused results: When I used threshold 1.3(0.05) in Monte Carol Null-Z Simulation, I didn¹t get any significant cluster. However when I used threshold 2(0.01), I did get one significant cluster. However I expected I at least got same significant area when I used lower threshold.
If I chose FWHM=10mm, I got another significant cluster when the threshold 1.3 was used, and got nothing when the threshold 2 was used. However this cluster is not the same area I got when FWHM=15mm was used.
At this point, I¹m totally confused, and don¹t know which one should be trusted. Should I used FWHM=10 or 15? Should I used threshold 1.3 or 2.0?
My group one have 49 subjects and group two have 46 subject. All subjects are males.
Hope someone can point the right direction for me. Thank you very much.
Wayne