On Wed, 21 Feb 2001, Karl Friston wrote:
> Dear Esa
>
> > Is the SPM correlation analysis appropriate for covariates of ordinal
> > measurements?
>
> Yes it is. In fact the general linear model does not distinguish
> between ordinal measurement or any other sort of explanatory variable.
> Strictly speaking SPM does not perform a correlation analysis - it is
> equivalent to a multiple linear regression. In this sense it is quite
> appropriate to regress your measured brain activity on any ordinal
> variable or some polynomial expansion of that variable.
>
> I hope this helps - Karl
>
Our covariate is clearly ordinal. Wouldn't it be better to use ordinal
correlation (e.g Spearman)? Does SPM (or some toolbox) provide a
solution for this?
Esa
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