Hi Professor Smith,
I meant the significant clusters of maxc image were distributed on right
side of brain, though uncorrected t-stat and single thresholded max image
showed relatively symmetric over both sides of hemisphere.
Thanks.
PHY
On Mon, 4 Jun 2007 07:34:01 +0100, Steve Smith <[log in to unmask]> wrote:
>Hi,
>
>On 3 Jun 2007, at 06:54, Ping-Hong Yeh wrote:
>
>> Dear FSLers.
>>
>> Our cluster output _maxc_ from randomise of comparing two groups
>> difference of tbss is very asymmetric,
>
>Do you mean the histograms from two opposite contrasts look very
>different or that a single histogram is not internally symmetric?
>
>The mapping from t to p, whilst one-to-one, is very nonlinear, so you
>wouldn't expect the histograms to look similar between t and p.
>Note also that t can be + or -, whereas p is from 0:1.
>
>I would not convert to z via p, I would use ttoz, but I wouldn't
>recommend this anyway - the only valid way to get cluster p-values in
>TBSS is via randomise, ie using the maxc images.
>
>Steve.
>
>
>> i.e. more significantly only one
>> side, though the uncorrected tstat is more bi-laterally. Any
>> explanation?
>>
>> I tried to convert the vox_tstat (1-p image) to z-stats using ptoz
>> and then
>> "cluster" the z-stats image through cluster command. The group
>> difference
>> results was more or less like tstat image, i.e.bilaterally symmtric.
>>
>> Would this approach make sense for doing the cluter-base
>> thresholding ?
>>
>> Thanks.
>> PHY
>
>
>------------------------------------------------------------------------
>---
>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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