Thanks, Steve!
On Sat, Feb 18, 2012 at 4:00 AM, Stephen Smith <[log in to unmask]> wrote:
> Hi
>
> On 17 Feb 2012, at 21:57, Klara Mareckova wrote:
>
> 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?
>
>
> correct - so they shouldn't really need to know the min cluster size -
> however you may as well answer their question.
>
> look in the report_log.html for the call to "cluster" and run it again by
> hand, using the
> --minclustersize
> option
>
> cheers.
>
>
>
> 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
>
>
>
> ---------------------------------------------------------------------------
> Stephen M. Smith, Professor of Biomedical Engineering
> Associate Director, Oxford University FMRIB Centre
>
> FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
> +44 (0) 1865 222726 (fax 222717)
> [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
> ---------------------------------------------------------------------------
>
>
>
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