Hello All,
I have a question about my design matrix for FSL’s randomise and hope to get your feedback on it.
The question here is to test the interaction between cognitive score and group (Group A and Group B).
I would like to control for study site (Site A and B), Sex and Age.
N = 50
3 groups
- Site (Site A x Site B)
- Sex (Males and Females)
- Group (A and B)
Continuous covariates
- Age (demeaned)
- Cognitive score (demeaned)
After looking at some examples on the FSL mailing list, I created the following matrix below:
Is that correct? Do I need really to split the groups by gender and site? I ask that because I have also seen quite a few other examples where nuisance categorical covariates were simply modelled as 1 and 0 in single columns.
Thanks in advance