# Re: st: Survival Analysis Issue (Again)

 From Allen Buxton <[email protected]> To [email protected] Subject Re: st: Survival Analysis Issue (Again) Date Thu, 25 Nov 2004 06:09:19 -0800 (PST)

```Without having checked Dr. Jenkin's code you might try
where there are about 270 thousand non-missing
observations. Something is causing the 'specification'
problem? ta drug age if _d==1 ... where _d==1, n=1343?

-Allen

--- Yaseen Ghulam <[email protected]> wrote:

> Dear Stata Users,
> I posted this request yesterday and have not got any
> response. I am posting it again.
> I am using stata routines to do survival analysis. I
> am interested in estimating expected
> and  median survival time for each person in the
> sample data. By following Professor
> Stephen P. Jenkins notes and codes and using
> duration data I got the following results.
>
> streg drug age, dist(weibull) nolog nohr
> predict xb, xb
> * median duration for each person in sample
> ge mediand = (ln(2)*exp(-xb))^(1/e(aux_p))
> * expected (mean) duration for each person in sample
>
> ge meand =
> exp(-xb/e(aux_p))*exp(lngamma(1+1/e(aux_p)))
>
>  Variable |       Obs        Mean    Std. Dev.
> Min        Max
>
-------------+--------------------------------------------------------
>
>           _d |        22    .8181818     .394771
>      0          1
>          _t0 |        22           0           0
>      0          0
>           _t |        22    12.77273    8.123639
>      1         32
>      mediand |  22     13.0186    3.276344
> 8.531759    19.7746
>        meand |  22    14.97909    3.769734
> 9.816569   22.75249
> This makes sense to me because median and mean
> duration min and max values are
> within the range of actual max value (_t).
>
> But when I am using exactly these codes on my data I
> am getting some values which
> are quite extreme. Am I making some mistake?
>
> Here are the results I am getting.
>
>     Variable |       Obs        Mean    Std. Dev.
>    Min        Max
>
-------------+--------------------------------------------------------
>
>           _d |    269512    .0049831     .070415
>      0          1
>          _t0 |    269512    10.33649    6.762769
>      0   28.32854
>           _t |    269512    10.41994    6.762693
> .0629706   28.41342
>      mediand | 269512    40.65339     63.9578
> .142106   1261.704
>        meand | 269512    69.90463    109.9772
> .2443553   2169.535
>
> Help Appreciatd.
>
>
> Yaseen
> University of Portsmouth
> *
> *   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/
>

*
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```