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Dear FreeSurfer experts,
I am doing a repeated measures ANOVA 2x2 (2 groups and 2 time points) and I would like to include in the analysis a covariate that is constant over the 2 times (e.g., baseline medication). I would like to see a "group x time x covariate" interaction.
What should the design look like? I know that without covariate the design is as follows:
GroupDescriptorFile 1
Class Subject1
Class Subject2
Variables Tp1vsTp2.Group1 Tp1vsTp2.Grroup2
Input Subject1_time1 Subject1 1 0
Input Subject1_time2 Subject1 -1 0
Input Subject2_time1 Subject2 0 1
Input Subject2_time2 Subject02 0 -1
Design matrix:
1 0 1 0
1 0 -1 0
0 1 0 1
0 1 0 -1
Contrasts (.mtx files): Tp1vsTp2.Group1 0 0 1 0 Tp1vsTp2.Group2 0 0 0 -1 Interaction (timexgroup) 0 0 1 -1
However, I do not know how I could include the interaction with that covariate.
Thank you very much in advance.
Kind regards,
Agurne