Dear Stata-listers,
A colleague of mine is asking about how to best interpret the "theta" value following the estimation of a "gompertzhet" model.
As an example, we have the following model:
xi:gompertzhet time i.sex i.tenureg i.newcohort i.marstat i.nmm i.socg i.educ i.bathg i.carg i.urind i.pob, dead(outcome) frailty(gamma) robust hr
log relative-hazard form Number of obs = 156134
Wald chi2(25) = 29045.86
Log likelihood = -173574.21 Prob > chi2 = 0.0000
------------------------------------------------------------------------------
| Robust
time | Haz. Ratio Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
_Isex_1 | 1.850406 .0142284 80.03 0.000 1.822728 1.878504
_Itenureg_2 | 1.149377 .0092286 17.34 0.000 1.131431 1.167608
_Itenureg_3 | 1.072943 .0094593 7.99 0.000 1.054563 1.091644
_Itenureg_4 | 1.642678 .037731 21.61 0.000 1.570366 1.718319
_Inewcohor~2 | 1.709805 .0201656 45.48 0.000 1.670735 1.74979
_Inewcohor~3 | 2.795179 .0342787 83.82 0.000 2.728795 2.863178
_Inewcohor~4 | 4.539291 .0613598 111.91 0.000 4.420607 4.661161
_Inewcohor~5 | 6.999815 .109719 124.14 0.000 6.78804 7.218198
_Inewcohor~6 | 13.94991 .2479541 148.27 0.000 13.4723 14.44445
_Imarstat_2 | .9453604 .010464 -5.08 0.000 .9250723 .9660935
_Imarstat_3 | 1.014716 .0123169 1.20 0.229 .99086 1.039146
_Imarstat_4 | 1.020194 .0325235 0.63 0.531 .9583996 1.085972
_Inmm_2 | 1.152044 .016659 9.79 0.000 1.119851 1.185162
_Inmm_3 | 1.284557 .015833 20.32 0.000 1.253896 1.315966
_Isocg_2 | .9955737 .0124997 -0.35 0.724 .9713737 1.020377
_Isocg_3 | .9578298 .0123819 -3.33 0.001 .9338665 .9824079
_Isocg_4 | .9479021 .0125159 -4.05 0.000 .9236861 .972753
_Ieduc_1 | 1.040396 .0106443 3.87 0.000 1.019741 1.061469
_Ieduc_3 | .9576366 .0229827 -1.80 0.071 .9136344 1.003758
_Ieduc_4 | .8596743 .0151121 -8.60 0.000 .8305596 .8898097
_Ibathg_2 | 1.139885 .0127556 11.70 0.000 1.115157 1.165162
_Icarg_0 | 1.121058 .008487 15.09 0.000 1.104547 1.137817
_Icarg_2 | .94181 .0123203 -4.58 0.000 .9179696 .9662695
_Iurind_2 | .9648657 .0075113 -4.59 0.000 .9502555 .9797004
_Ipob_2 | .9581827 .0144905 -2.82 0.005 .9301987 .9870086
-------------+----------------------------------------------------------------
gamma | .0080562 .0000682 118.09 0.000 .0079225 .0081899
/ln_the | -1.996373 .0600449 -33.25 0.000 -2.114059 -1.878687
-------------+----------------------------------------------------------------
theta | .135827 .0081557 .1207469 .1527906
------------------------------------------------------------------------------
We found a great deal of help in understanding the gompertz model from the book "Introduction to Survival Analysis Using Stata" by Cleves,Gould and Gutierrez. But, there seems to be very little explanation of how to use and interpret the "theta" coefficient estimated by the model.
Many thanks for your help in advance.
Best wishes,
Amani
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