I have a found the effect of my factor A (which has three levels; one for each
group of subjects). Additionally, I found the effect of a covariate (a
neuropsychological score). All effects are second-level.
How can I now figure out, if the correlation with the covariate is different for
the levels of factor A (three groups of subjects; different corralations with the
covariate in each group of subjects). I was thinking of calculating the
interaction between factor A and my covariate, but I can neither figure out
how to do this in SPM5 nor if this is the correct approach.
Thanks alot for your help!