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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 > -- ------------------------------------------------------------------------------- Tim Behrens Centre for Functional MRI of the Brain The John Radcliffe Hospital Headley Way Oxford OX3 9DU Oxford University Work 01865 222782 Mobile 07980 884537 -------------------------------------------------------------------------------