Without having checked Dr. Jenkin's code you might try
restricting your streg to a subset of your dataset
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
> *
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> *
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>
*
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