Hi,
On 19 Nov 2008, at 05:26, liang wang wrote:
> Hi FSLers
>
> If I would investigate the relationship between FA values in the
> skeleton voxels and multiple behavioral data together, I need to
> manually generate the design.mat and design.com files. However, I
> don't know how to set the parameters: PPheights in the two files and
> what roles the parameters in randomize process.
Don't worry about these - you can just set to 1 or leave this line out
of the header - randomise doesn't use it.
> Also, if I want to select the cluster-based thresholding corrected
> for multiple comparisons, how to set the required t (or F) value. At
> present, according to the no corrected results (e.g.
> file_vox_corrp_tstat.nii.gz obtained from 5000 randomize times),I
> select a threshold corresponding to the considered significant level
> (e.g. p < 0.001). Thus, using the threshold for t or F contrast (a
> parameter of -c or -C), I rerun the whole analysis procedure. I
> don't make sure whether the selection step is suitable.
Indeed - that's the problem with cluster-based thresholding - there's
no principled way of choosing the initial cluster-forming threshold.
You might like to try some arbitrary threshold like 2.3 (or 0.000023
or 23000), which seems popular; alternatively you can try using TFCE
instead, which gets around this problem, by setting the -T option
instead of -c.
Cheers.
> I am appreciated for any suggestion.
>
> Best
> Liang Wang
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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)
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