Hello,
I've run a group analysis for my data using cluster thresholding
(z=2.3, p=0.05 in the poststats). I was asked to clarify 1) the
correction for multiple comparisons used and 2) what is the minimal
number of voxel required for the cluster threshold.
Woud the correct answer for 1) be I've used cluster based thresholding
in FSL: First thresholding voxelwise images at z=2.3 and then applying
Random field thory to keep only those clusters that are big enough for
the z to ensure an overall (familywise) p<0.05? Or do I need to add
anything else?
2) I don't know how to calculate the minimal number of voxels required
for the cluster threshold. Is there any formula or tables to find out?
(I was trying to read up and found that z=2.3 might correspond to 76
voxels but I'm not sure whether this is also correct for my case and
how to verify.)
Thanks a lot for your help,
Klara
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