st: Confidence Intervals and Survival Estimation using Weights

[Nicolás Rojas <nicolas.srojas@gmail.com>]

Dear STATA users,
                                      I am computing Kaplan -Meier
estimators for the probability that teachers stop working and I have
had many problems while working with pweights.

1) Does anybody knows how to compute  confidence intervals for Kaplan
Meir survival curves?? For some mysterious reason confidence intervals
are computed when data is unweighted but when applying weights they
disappear. Also most of the hypothesis test are disabled along with
confidence interval estimation and interval plots.

2) Does anyone knows how to overlay many KM graphs??? Even though the
help says that addplot is possible, an error appears anytime one tries
to use this feaure: "sts is not a twoway plot type".  I thought that
one option was just using sts list to tabulate the results and the
plotting them but using the line comands gives plots quite different
from what is usually shown  with sts graph.

Thank you very much, best,

Nicolás Rojas
Research Assistant
Ponitificia Universidad Católica de Chile

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