# Re: st: predict or adjust after logistic?

 From Joanne Garrett To statalist@hsphsun2.harvard.edu Subject Re: st: predict or adjust after logistic? Date Thu, 03 Apr 2003 10:00:08 -0500

```predxcat and predxcon use the strandard error of the prediction. I plan
to update these programs to take advantage of the Stata 8.0 graphics as
soon as possible (in otherwords, when I figure out how to do it), and
will post them for anyone who is interested.
Joanne Garrett

"Daniel, Gregory" wrote:
>
> I have just tried using the predxcat command, but I noticed that the
> confidence intervals seem too narrow and are pretty much the same as the
> CI's obtained when using:
>
> Adjust x2 x3 x4, by(x1) pr ci
>
> These CI's are calculated using the standard error from the predicted index,
> not the predicted probability---correct?
>
>
> Christer wrote:
>
> Check out
> Predxcon or predxcat
> or
> logpred , regpred
> or
>
> The commands at Scott Long's Homepage (http://www.indiana.edu/~jslsoc/)
>
> Greg wrote:
>
> To predict  probabilities and 95% CIs of the predicted probabilities after a
> multivariate  logistic model, I have previously used the following predict
> command:
>
> logistic y x1 x2  x3
> predict lr_index,  index
> predict se_index,  stdp
>
> gen p_hat =  exp(lr_index)/(1 +exp(lr_index))
> gen lb = lr_index -  invnorm(0.975)*se_index
> gen ub = lr_index +  invnorm(0.975)*se_index
> gen plb =  exp(lb)/(1+exp(lb))
> gen pub =  exp(ub)/(1+exp(ub))
> bysort x1: tabstat  p_hat plb pub
>
> However, this code  does not allow me to predict probabilities,
> by(x1), while keeping the other  covariates held constant, as the adjust
> command does.
>
> *
> *   For searches and help try:
> *   http://www.stata.com/support/faqs/res/findit.html
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```