This appears to be correct. The corrected FWE cluster p-values do not
depend on your data. They depend on the smoothness of the data (this
is the same for all contrasts within the GLM - although not true for
GLM Flex), the voxel p-value threshold (u) and the corrected cluster
p-value (alpha). It also depends on the number of resels, which is the
same for all contrasts in your model.
The difference between Tom's program and the output at the bottom of
SPM is that SPM chooses the smallest cluster extent that is below
cluster-FWE 0.05. If you get threshold from Tom's program or SPM, the
results will be the same. The inferences you will make will be the
same. Tom's program simply tells you the true minimum cluster compared
to SPM that tells you the minimum in your current contrast.
Peak_nii uses the same approach as SPM in determining the cluster extent to use.
Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Postdoctoral Research Fellow, GRECC, Bedford VA
Website: http://www.martinos.org/~mclaren
Office: (773) 406-2464
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On Wed, Feb 13, 2013 at 5:38 AM, P Andersson <[log in to unmask]> wrote:
> Hi all,
>
> I have a question regarding the CorrClusTh code (kindly provided by Tom Nichols).
> As I understand it the program does not use the actual data, only info regarding smoothing and resolution etc.
> In other words, all contrasts computed using the same GLM setup would get the same cluster-size limit.
> Is this correct, and if so, does it make sense?
>
> Thanks!
> Patrik
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