Dear FS list,

I have a data set with 3 groups (2 treatments, 1 control), each with equally-spaced time-points (pre and post structural scan). I've done the 3 longitudinal pre-processing steps, and stage#1 of the two-stage model, and I would prefer to run stage#2 (cross-sectional analysis of the difference) with QDEC as opposed to with mri_glmfit.

I know that QDEC is meant for 2 groups, but I see that designs with 4 or 6 groups can be analysed with QDEC (as per this FSGD examples page) whereas designs with 3 groups cannot be. It seems to me that an even number of groups is QDEC-able while an odd number isn't, but is there any workaround so that I can still use QDEC? Perhaps if I only do pairwise comparisons one at a time, i.e. treatment1 vs control and treatment2 vs control?

Many thanks!