Dear SPM experts,
Sorry for such basic questions. I'm new to the longitudinal design and analysis, and I have some doubts I would like to clear.
I have two groups of 12 subjects each and a follow-up MRI of two years for each subject.
Factor 1 (group) : 2 levels (Gp1 and Gp2)
Factor 2 (longitudinal) : 2 levels (year1 and year2)
A) As I undesrtood I have to set a full-factorial 2x2 anova (Group x Follow-up MRI as above), but I've seen in some faqs that I actually have to set up a third factor "subjects" which is the number of subjects in my study, but as I have never set a full factorial design, I'm not sure on how to set this third factor.
B) How and which would be the constrasts for the desing in A? I mean, to test the effect of the groups and/or the differences in year1 and year2.
C) Is it possible to introduce nuisance variables i.e. age in year1 and age in year two?
D) how do I correlate any of the tested effects with a variable of interest?
Many thanks in advanced,
Gabriel