Hi list,

I'm performing cortical thickness among 3 groups by using GLM.

I created a group descriptor file with 3 groups and 2 covariates (age and mean thickness).

I performed 3 comparisons A-B, A-C, B-C.

Now, for one of 3 groups (group C) I have:

groups C=30 subjects; I'd like to divide it in some pairs.

First pair: X (n=15) vs Y (n=15). Second pair: Z (n=15) vs W (n=15). Between first and second pair there isn't interactions.

X or Y subgroup can contain also subjects included in Z or W.

Z or W subgroup can contain also subjects included in X or Y.

Design:

group A

group B

subgroup X vs subgroup Y

group C ------<

subgroup Z vs subgroup W

I'm thinking to perform qdec for X-Y and Z-W. Is it correct?

What do you advise me?

Thanks,

Stefano