Hi - randomise _is_ nonparametric.....
Please read the randomise manual - if you load in the *corrp* image
into FSLView and threshold at 0.95, that gives you p<0.05 corrected.
Cheers.
On 10 Aug 2009, at 16:15, Kirsi Kinnunen wrote:
> Hello dear FSL users!
>
> Would anyone be as kind as to share their wisdom on TBSS statistical
> analysis with me? I am new to both FSL and TBSS and wanted to check
> if it's
> possible to do what I want to do.
>
> I am interested in testing for a correlation between FA (and mean,
> axial and
> radial diffusivity) and a behavioural measure that I don't think
> necessarily
> is parametric by its nature.
>
> So far I have only been able to test for the correlation using
> randomise
> because I'm not aware of equivalent nonparametric methods. I'm
> pretty sure
> that the design is fine as it is but the actual stats command is
> what I'd
> really appreciate some help with. The command I've used to do the
> stats so
> far is:
>
> randomise -i all_FA_skeletonised -o newfilename -m
> mean_FA_skeleton_mask -d
> design.mat -t design.con -n 5000 -x -V (for voxelwise stats that I
> then
> threshold appropriately using fdr)
>
> OR
>
> randomise -i all_FA_skeletonised -o newfilename -m
> mean_FA_skeleton_mask -d
> design.mat -t design.con -n 5000 --T2 -V (tfce thresholded images)
>
> Q1: How would I modify the above to do nonparametric stats instead?
>
>
> The other thing that puzzles me is thresholding, and hence the
> following
> question.
>
> Q2: How does the thresholding such as the above relate to
> thresholding done
> in fslview when looking at the result? That is, once I've
> thresholded the
> results using tfce or fdr correction, do I still have to adjust the
> threshold in the fslview window e.g. from 0.949 to 1 to get to p< .
> 05 or
> 0.999 to get to p< .01 ?
>
> Sorry if these questions seem silly, but I would very greatful for
> any help.
>
> Kind regards,
> Kirsi
>
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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)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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