I don't think you are modeling gender and scanner appropriately. It
looks like you have them as continuous covariates? The right way is to
create classes. In your case, you'd have 8 classes, Group1MaleScanner1,
Group1FemaleScanner2, etc.
On 09/15/2016 10:48 AM, Eryilmaz, H. Hamdi wrote:
>
Dear Doug/FreeSurfers,
We are looking at effects of age-squared on cortical thickness in two different
groups. We are interested in age-squared by group interactions on cortical
thickness across the surface. Nuisance covariates include age, sex, scanner,
and total brain volume.
The sig map
