Hi all, I'm running analyses in Qdec and want to verify a few things:
1. When comparing two groups (HC vs patients) I am including mean cortical thickness as a covariate, using the following equation: bh.thickness = (lh.thickness*lh.surfarea + rh.thickness*rh.surfarea) / (lh.surfarea + rh.surfarea) Is this the best way to calculate global mean thickness? 2. I want to regress out any effects of age, therefore I need to demean the ages for my groups as a whole, and not perform this calculation on each group separately, correct? 3. I'm including questionnaires as a covariate of interest - do I need to demean these values as well? Thank you in advance for your help! Ashley -- Ashley A. Shurick Ph.D. Candidate Department of Psychology Stanford University
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