Hi Stata people:
this is more of a statiscal question, but involves using Stata for obtaining
the results, so I felt I could post it here.
I have survival data for treatment 1 and treatment 2 and Kaplan Meier curves
cross; the test for the interaction treatment*time is highly significant. I
am not interested in spliting the time in two periods, before and after the
crossing, for two pair of curves (PH treatment 1 vs treatment 2 before the
crossing, plus another diferent PH treatment 1 vs treatment 2 after the
crossing), which is the solution given in the text book of Klein &
Moeschberger for the data set ot cateter.
I would like to use the results of _stcox interaction, bases(s0)_ after
spliting the data. I am doing something really wrong. I _gen
s1=s0^(interaction^time)_ but, although s0 and s1 do cross at the observed
time of crossing in KM curves, the s1 curve goes up and up as time
increases, which of course is wrong. Probably my _gen s1_ definition is
wrong, but I failed in finding the error.
Thank you for any help.
Jose Maria
Jose Maria Pacheco de Souza, Professor Titular
Departamento de Epidemiologia/Faculdade de Saude Publica, USP
Av. Dr. Arnaldo, 715
01246-904 - S. Paulo/SP - Brasil
fones (11)3082-3886; (11)3066-7724; (11)3768-8612; (11)3714-2403
fax (11)3082-2920; (11)3714-2403
www.fsp.usp.br/~jmpsouza
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