> However, given that the units I am comparing are Fisher-transformed z-scores
> of correllations, I don't know how to make sense of the magnitude of these
> results. How can I interpret these units?
You can convert those z-scores back to correlation coefficients through the following
3dcalc -a Grp_Result+tlrc'[0]' -expr '(exp(2*a)-1)/(exp(2*a)+1)' -prefix GrpR
Gang