No, I am referring not to a t or z score, but to a regression weight.
A standardized Beta weight is never greater than one. It is a 'factor
loading' so to speak.
Ed
On Tuesday 12 August 2003 01:16 am, Tim Behrens wrote:
> Hi there - by standardised beta weight, do you mean the t-statistic?
>
> You can get these post-hoc using Feat, by just running the
> contrast-manager (by selecting Post-Stats from the top right menu,
> clicking on the Post-Stats tab, and selecting "Edit Contrasts").
>
> If you want to get them by hand, you were nearly right, you have to
> divide the copes by the square root of the varcopes (i.e. the standard
> error on the copes).
>
> If you want them to be truly sandardised (i.e. z-scores), you have to
> account for the degrees of freedom, you can do this with ttoz
>
> ttoz -zout zoutput varcope cope dof
>
>
>
> Hope this answers your question
>
> cheers
>
> Tim
>
> On Mon, 11 Aug 2003, Edward Vessel wrote:
> > Hi folks -
> >
> > How would one go about computing a standardized beta weight (in the
> > regression sense) from a cope or pe?
> >
> > If I am correct, the pe's are (unstandardized) regression weights (b's).
> > Therefore, I'd need to multiply by the standard deviation of the
> > predictor and divide by the standard deviation of the data. But I am
> > unsure which files would correspond to this.
> >
> > The varcope seems to be not just be the deviation of the predictor, as
> > that should be the same for all voxels. It also isn't the standard
> > deviation of the data, as this would be the same for all predictors. Is
> > it a ratio of the two?
> >
> > If that is the case, then do I just divide the cope by the varcope to get
> > a standardized weight?
> >
> > I'm not interested in getting percent signal change in this case ... it
> > is a continuously varying parameter (from 0 to 1), so I'd like to get a
> > beta weight (or even part correlation).
> >
> > Ed
> >
> > --
> > Ed Vessel
> > U. of Southern California [log in to unmask]
> > Dept. of Neuroscience
> > HNB, 3641 Watt Way http://geon.usc.edu/~vessel
> > Los Angeles, CA 90089-2520
> > (213) 740-6102
--
Ed Vessel
U. of Southern California [log in to unmask]
Dept. of Neuroscience
HNB, 3641 Watt Way http://geon.usc.edu/~vessel
Los Angeles, CA 90089-2520
(213) 740-6102
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