afni.nimh.nih.gov

If I can use the" 3dcalc" to calculate the subject.niml.dset file, so that I can get mean value at each node from a group of subjects.
Is it right to use it as followed:
3dcalc -a Subject1.niml.dset[6] \
-b Subject2.niml.dset[6] \
.
.
.
-expr mean(a,b,...)
-prefix mean_suject.niml.dset
I want to know if I need to get the certain columns as the input or just use Subject1.niml.dset. as the input. And if I want to do the 3dttest, at this time, the input is Subject1.niml.dset.?