afni.nimh.nih.gov

The error message is not a little strange. You only have 3 subjects in each group? Plus, these are the centered values of the age and bmi?

9 centered values for numeric variable age : -1 0 1 -1 0 1 -1 0 1
9 centered values for numeric variable bmi : -1 0 1 -1 0 1 -1 0 1

Gang