Dear Carles,
If you have specified the error variances to be different between the
groups (using the nonsphericity options) then, in principle, it should be
possible to recover images of standard deviations.
But this is'nt a standard option within SPM.
You'll have to use a
combination of the residual variance images (ResMS.img),
the 'hyperparameters' relevant to each group (in SPM.xVi.h)
and, possibly, the numbers of subjects within each group.
Have a look in the help for spm_spm.m for how you might go about doing this.
Alternatively, you could look at the ResMS images obtained from
two separate one-sample t-test analyses (you may need to normalise
wrt. the number of subjects in each group - have a look in spm_spm.m
to check).
Best,
Will.
CARLES M. FALCON FALCON wrote:
>
> 2)In a 2 sample T-test analysis, it is possible to get an image of the standard
> desviation of each group?
>
> Thank you very much for your help
>
> Carles Falcon
> University of Barcelona
>
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--
William D. Penny
Wellcome Department of Imaging Neuroscience
University College London
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London WC1N 3BG
Tel: 020 7833 7475
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URL: http://www.fil.ion.ucl.ac.uk/~wpenny/
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