Hello Freesurfers,

My apologies for this very basic question more about statistics than freesurfer, but I have not found an answer anywhere on the wikis, or the web (maybe it is too basic :-) )  I am interested in age-related effects of hiv and I wanted to covary for age and education in mri_glmfit.  For example, if my fsgd file is:

class control
class hiv
variables age ed
input subj1 control 40 13
input subj2 hiv 35 12
...
...

and I use dods, is my contrast matrix the place where I would tell it to covary?  Something like:
0     0        -1     1           1     1                1     1
(y-int)     (age slope)   (covary for age)   (covary for ed)

As always, thank you for your help,
Jeff

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