Dear Denise,
If your GLM analysis used a design matrix with a single regressor,
there is a 1 to 1 relationship between the correlation
coefficient, r, (of regressor and data) and regression coefficient, beta,
which is
r = beta * s_x/s_y
where s_x is the standard deviation (SD) of the regressor and
s_y is the SD of the data.
If beta is inferred to be significantly non-zero, using eg. a t/F-test,
then r is guaranteed to be significantly non-zero.
If your GLM analysis contains a design matrix with multiple
regressors, as is usually the case, then there exists a one
to one relationship between each regression coefficient
and its corresponding *partial* correlation coefficient, rp, ie.
the correlation between that regressor and the data after having
subtracted from the data what can be explained by the other regressors.
Again, if the regression coefficient is inferred to be significantly
non-zero then rp will also be.
But there's no easy way of getting the r/rp values out of SPM2.
You'll have to matlab it.
Best,
Will.
Denise Dörfel wrote:
> Hi SPM users,
>
> I did a correlation analysis between the activation of a contrast and
> the score of a questionnaire.
> Is it possible to show the correlation coefficient or to get it out of
> SPM2?
>
> In general, how can I get infos like this out of SPM2?
>
> Thanks in advance.
> Denise Dörfel.
>
--
William D. Penny
Wellcome Department of Imaging Neuroscience
University College London
12 Queen Square
London WC1N 3BG
Tel: 020 7833 7475
FAX: 020 7813 1420
Email: [log in to unmask]
URL: http://www.fil.ion.ucl.ac.uk/~wpenny/
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