On Thu, 4 Dec 2003, Peter Dalgaard wrote:
> Prof Brian Ripley <[EMAIL PROTECTED]> writes:
>
> > > report. In the Stata output, they report alpha, same as 1/theta from
> > > the R glm.nb output. Except for minor differences in standard errors,
> > > only the intercept estimates markedly differ.
> >
> > What are the variable codings used? Intercepts depend on coding of
> > factors, and that applies to any sort of regression.
>
> ..and the fact that the difference between the two intercepts equals
> the gender effect quite strongly suggests that Stata has gender coded
> 1 for females and 2 for males.
>
and this turns out to be the case.
In stata after fitting the model
lincom _cons+gender
( 1) [daysabs]gender + [daysabs]_cons = 0
------------------------------------------------------------------------------
daysabs | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
(1) | 2.716069 .232576 11.68 0.000 2.260229 3.17191
------------------------------------------------------------------------------
which agrees almost exactly with the R intercept.
-thomas
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