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/
