Hello,
I am analyzing a factorial design. After FWE correction, I obtained a
significant main effect of a 3-levels factor (F test). I would like to
run some post-hoc contrasts within the significant-F region (a few
clusters), to test for pairwise differences between the various levels
of the design factor.
My question: is it appropriate to carry out the post-hoc contrast by
using the same FWE correction (computed considering the entire brain)
when my interest is in a rather restricted area? Don't I run the risk of
being too conservative and/or imprecise?
Can someone please suggest the standard approach in this case? Should
one re-estimate the proper FWE correction by re-running the factorial
model within the regions of interest?
Cheers,
Bruno
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