[R] calculating dispersion formula using deviance ( was Re: (no subject) )

Adaikalavan Ramasamy ramasamy at cancer.org.uk
Mon Jul 11 12:19:16 CEST 2005

Please try to use a meaningful subject line. See below for comments.

On Mon, 2005-07-11 at 11:30 +0200, Smit, R. (Robin) wrote:
> Hello,
> The estimate of glm dispersion can be based on the deviance or on the
> Pearson statistic.
> I have compared output from R glm() to another statastical package and
> it appears that R uses the Pearson statistic.

A quick search would also highlight the following thread

> I was wondering if it is possible to make use R the deviance instead by
> modifying the glm(...) function?

I don't know what the formula for using the deviance is but _IF_ it is
the square root of ratio of null deviance by its degrees of freedom,
then sqrt( fit$deviance / fit$df.null ) should be useful.

> Thanks for your attention.
> Kind regards,
> Robin Smit
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