Dear CONN users/experts,

I have two groups (group_F, group_M; n = 35), however, only 30 subjects have a behavioral measure of interest. After comparing between group differences, I am interested in the interaction model. For simplicity, I am using 6 subjects as an example (subject 5 does not have behavioral measure) and want to check whether I am doing it correctly or not.

group_F = [1 1 1 0 0 0]
group_M= [0 0 0 1 1 1]
covariate1 =[-2 -1 -0.5 0.5 1 2] #Demeaned (a.k.a., orthogonalized for all subjects)
trait_F = [x1 x2 x3 0 0 0]
trait_M= [0 0 0      y1 0 y2] #Note the fifth subject being zero in both trait_*

This is the contrast that I should use for the model below: [0 0 0 1 -1]
y ~ group_F + group_M + covariate1 + trait_F + trait_M

Three questions:
1. Am I doing all things right?
2. Do I need to also orthogonalize trait_F & trait_M? In respect to all subjects? or in respect to group_F and group_M, respectively?
3. Any positive t-stat result for this contrast (trait_F > trait_M) means that there is a significant group*trait interaction in that voxels (regression lines of activity ~ trait for each group are crossing each other for that region), in which there is a positive beta for activity~trait in group_F and negative beta for activity~trait in group_M, right?


Thanks in advance!

Bests,
Amir