Dera Eric & Griselda
I think this is the correct approach in SPM99 - enter the "single-subject
covariates only" (in PET/PSECT toolbox). This equivalent analysis seems
to work.
Regards - Mike
--
---------------------------------------------------------------
Mike Glabus, PhD
Visiting Fellow in Functional Neuroimaging
Unit on Integrative Neuroimaging
Clinical Brain Disorders Branch, NIMH, NIH
Building 10, Rm 4C101, 9000 Rockville Pike
Bethesda, MD, 20892-1365, USA
Tel: + 301 496 7864 FAX: + 301 496 7437
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> -----Original Message-----
> From: ERIC ZARAHN [mailto:[log in to unmask]]
> Sent: Tuesday, February 08, 2000 12:16 PM
> To: [log in to unmask]
> Cc: [log in to unmask]
> Subject: Re: unestimable block effects and segmentation fault
>
>
>
> Griselda,
>
> As Jesper implied, your covariate of interest is linearly
> dependent with subject effects, preventing the unique
> estimation of either.
> The only way to estimate the partial slope on your covariate
> of interest
> with the type of design you have (which I am presuming is one
> scan per subject)
> would be to not include subject effects in your model. This would
> effectively treat subject effects as error components. I am
> not precisely
> sure how to implement this in SPM, but my guess would be to "pretend"
> (in the context of SPM) that all of the data was from a
> single subject.
>
> Sincerely,
> Eric
>
>
> Eric Zarahn
> University of Pennsylvania
>
>
> >
> > Dear SPM'ers
> >
> > We have tried to use SPM99 to investigate linear
> correlations between
> > regional brain uptake of SPECT tracer in our psychiatric
> samples (OCD
> > and major depressive patients) and the severity of symptoms
> as assessed
> > using standardized rating scales.
> >
> > We have attempted a design that used to work with SPM96, which is
> > "multi-subject: covariates only" but this did not work now (error
> > message: "unestimable block effects"). We have also attempted the
> > "single subject: covariates only" option with no success either
> > ("segmentation fault").
> >
> > I wonder if we could have some help on that. Many thanks...
> >
> > Griselda Jara Garrido
> >
>
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