Dear FS experts,

I would like to test if the correlations between thickness/area and cognition differ between two groups, while age, socioeconomic status (continuous) and gender (dichotomous) should be nuisance variables.

To look at the effect of cognition in one group only, I made a model with 8 regressors:

- sex male
- sex female
- age male
- age female
- cognition male
- cognition female
- ses male
- ses female

With the contrast 0 0 0 0 0.5 0.5 0 0: how does cognition correlate with Cth/CSA, controlled for age, sex, and ses.

Now how do I model this, if I have two groups and want to look at the interaction of group*cognition? I have trouble setting up the fsgd and design matrix.

Any help is appreciated,

Thanks in advance,

Ines