Dear spmers,
in a VBM analysis I am performing, the total intracranial volume (TIV) has notable collinearity with group defining variable (different mean value of the TIV in each group). Is it valid to orthogonalize both regressors (group and TIV) to remove this collinearity?
Many thanks
Carles Falcon
Medical Image Lab. IDIBAPS
GIB-UB. CIBER-BBN. Barcelona
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