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RE: st: Confidence limits on survival probabilities from stcox

From   "CDSC - Verlander, Neville" <>
To   "''" <>
Subject   RE: st: Confidence limits on survival probabilities from stcox
Date   Tue, 1 Feb 2005 10:01:26 -0000

Dear stata users

Thanks for Ricardo's idea, but there are two problems: one that the
estimates obtained are not the same as those that stcurve plots (perhaps the
fact that my covariates are categorical variables with more than 2 levels I
may have used the adjustfor option in the wrong way - I put in the dummy
variables, except the baseline ones - so I stand to be corrected on this
one) and two, that one only gets a listing at the time points in the dataset
and not at all the time points.

Here is a snippet of code which gives one of the graphs with 8 curves
corresponding to the 8 sizegroups (similarly for the other 12 countries).
Regarding point one, I can't reproduce the values in the output file
cox1.dta using the sts list command - I've tried using both the by and
adjustfor commands. Assuming one can reproduce the values, how does one
overcome point two above? 

xi i.sizegrp i.cogrp;
ren _Isizegrp_2 s2;
ren _Isizegrp_3 s3;
ren _Isizegrp_4 s4;
ren _Isizegrp_5 s5;
ren _Isizegrp_6 s6;
ren _Isizegrp_7 s7;
ren _Isizegrp_8 s8;
ren _Icogrp_2 c2;
ren _Icogrp_3 c3;
ren _Icogrp_4 c4;
ren _Icogrp_5 c5;
ren _Icogrp_6 c6;
ren _Icogrp_7 c7;
ren _Icogrp_8 c8;
ren _Icogrp_9 c9;
ren _Icogrp_10 c10;
ren _Icogrp_11 c11;
ren _Icogrp_12 c12;
ren _Icogrp_13 c13;
stcox s2 s3 s4 s5 s6 s7 s8 c2 c3 c4 c5 c6 c7 c8 c9 c10 c11 c12 c13, robust
         survival outfile(c:\work\data\cox1.dta,replace)
title("Country 1",size(medium) color(black)) xtitle("No. of weeks")
legend(label(1 "Sizegroup 1") label(2 "Sizegroup 2")
label(3 "Sizegroup 3") label(4 "Sizegroup 4") label(5 "Sizegroup 5") 
label(6 "Sizegroup 6") label(7 "Sizegroup 7") label(8 "Sizegroup 8"));

Once again, thank you for your attention and any assistance you can provide.




Neville Verlander
Statistics Unit
Statistics, Modelling and Economics Department
Health Protection Agency Centre for Infections
61 Colindale Avenue

Tel: (direct) (+44) 0208 3277426
Fax: (+44) 0208 7868

-----Original Message-----
[] On Behalf Of Ricardo Ovaldia
Sent: 31 January 2005 17:00
Subject: Re: st: Confidence limits on survival probabilities from stcox

--- "CDSC - Verlander, Neville"
<> wrote:

> How can one obtain the 95% confidence limits on the survival 
> probabilities from multiple failure data following model estimation 
> using stcox and how is it different if one wants, say, a 70% 
> Confidence Interval? I know one can use sts list, but this only gives 
> Kaplan-Meier estimates giving quite different estimates to those from 
> stcox.

I think that you can use the -sts list- with the -adjustfor()-. Acording to
the help file it fits a Cox model.


Ricardo Ovaldia, MS
Oklahoma City, OK

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