Dear FreeSurfer experts, I would appreciate a confirmation regarding correctness of my approach.
I am trying to run an LME model for three groups (group1=controls, group2 and group3) and two time points. I followed the tutorial on https://surfer.nmr.mgh.harvard.edu/fswiki/LinearMixedEffectsModels <https://surfer.nmr.mgh.harvard.edu/fswiki/LinearMixedEffectsModels> and adapted the four group example. However, I am not 100% sure if my adaption is correct and would appreciate your input. The design matrix for the model contains the following columns: 1) Intercept 2) time (tij) 3) one for Group2 and zero otherwise 4) column 3) .* time 5) one for Group3 and zero otherwise 6) column 5) .* time To test the null hypothesis of no group differences in the rate of change over time among the three groups I applied the following contrast: 0 0 0 1 0 0 0 0 0 -1 0 1 Is this contrast correct? In a second step, I would use the additional three contrasts to identify which groups were different: 0 0 0 1 0 0 and 0 0 0 0 0 1 and 0 0 0 -1 0 0 1 I really appreciate your help! Best wishes Sarah
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