I don't think there is a standard way to do this. A vertex-wise analysis is not
the same thing as a averaging over a group of vertices. I guess you could
constrain your post-hoc analysis to be within the main effect cluster; that
would be most consistent. But I don't think you'd have any problems getting it
published either way.
On 12/2/2019 3:12 PM, cody samth wrote:
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Hi,
I have a statistical question about how to approach reporting results from
FreeSurfer analyses containing three groups. I ran a group effect (F-test) and
then post-hoc tests looking at pair-wise comparisons between the three groups.
My question is why is that we run separate vertex-wise analyses for the
post-hocs rather than extracting the values from significant clusters and
running post-hocs in a statistical software for just the regions where a
significance difference was found (ie the clusters)? As a post-hoc vertex wide
analysis can lead to different results.
For example in my group effect contrasts I found a cluster in the parietal
lobe. Whereas in my post hoc-vertex wide analyses one of them found two
clusters 1) within the parietal 2) within the frontal lobe. If I choose to run
these post-hoc analyses via freesurfer (ie vertex-wise) rather than extracting
the results to analyze in a statistical program, is it standard to report the
second cluster? Even though it didn't come up in the group model? If so is
there a paper that people reference that uses this approach?
Thanks,
Cody
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