Dear Experts,
I would like to perform a repeated measures analyses on white matter data processed through TBSS and grey matter data processed in FSLVBM using randomise. I have two groups each scanned three times (1) baseline, 2) after a three month intervention, and 3) four months later as a followup). The data set is complete, without missing data. Furthermore, I want to use demeaned age as a covariate of non-interest and test if there is a change within and between group over time.
My first issue is that I get an error that my model is rank deficient because at least one EV is a linear combination of the others. I am assuming this is due to the age covariate. Are there ways around this, possibly using a more separable metric of age?
Secondly, is the aforementioned design feasible in randomise?
Thanks in advance for the help,
James
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