[Freesurfer] Disentangling age effects

Hi,

I am studying two groups and have found that age is a confound (or is a covariate with an interaction between the two groups). Simply, when I correlate age between the two groups, there is an interaction (i.e., the slopes are different).

My questions are:

1) is it appropriate to proceed with a map-wise t-test (with or without age as a nuisance covariate)? 2) is there a way to pull out age effects on each group specifically, i.e., use age as a covariate of interest?

If neither of these methods is statistically sound, is there a method that can be used to describe age effects in each group, or characterize the findings?

Thanks,

Massih Moayedi