# RE: st: RE: RE: CIs for the ratio of two adjusted predictions after logistic?

 From "Nick Cox" To Subject RE: st: RE: RE: CIs for the ratio of two adjusted predictions after logistic? Date Wed, 1 Aug 2007 17:34:37 +0100

```Got it.

Nick
n.j.cox@durham.ac.uk

Maarten buis

> --- Nick Cox <n.j.cox@durham.ac.uk> wrote:
> > I think in this the term
> >
> > _b[foreign]
> >
> > should be
> >
> > _b[foreign] * foreign
> >
> > and that
> >
> > _b[foreignXmpg] * mpg
> >
> > should be
> >
> > _b[foreignXmpg] * foreignXmpg
>
> No, I am comparing for each value of mpg the predicted probability of
> foreign cars with the predicted probabilities of domestic cars. To do
> so I create a local `xb_for' which contains the linear predictor
> assuming the car is foreign and a local `xb_dom' which contains the
> linear predictor assuming that the car is domestic. (actually the
> locals contain the commands that will create the linear
> predictors, but
> that is a detail) Consider the code for the linear predictor assuming
> that the cars are foreign.
>
> #delim ;
> local xb_for "_b[_cons] + _b[foreign] +
>               _b[mpg]*mpg + _b[foreignXmpg]*mpg" ;
> #delim cr
> In that case we know that the the variable foreign has value 1, so
>
> _b[foreign]*foreign =
> _b[foreign]*1 =
> _b[foreign]
>
> similarly:
>
> _b[foreignXmpg]*foreign*mpg =
> _b[foreignXmpg]*1*mpg =
> _b[foreignXmpg]*mpg
>

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```