[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

From |
Mark Trappmann <[email protected]> |

To |
[email protected] |

Subject |
st: one-sample logrank test |

Date |
Mon, 16 Jan 2006 16:19:06 +0100 |

Dear list members,

I am currently trying to calculate a one-sample logrank-test (Gail & Ware 1979, Woolson 1981) for a test of equality between the survivor function of a sample and that of the corresponding population.

I have searched the stata-list archives and the User Group Meetings and came up with 2 results - which are both not satisfactory:

1.) I found a presentation by Pere�Joan Ventura on a User Group Meeting in Spain. There is mentioned a Do-File onesam.do for this purpose, which I cannot find anywhere in the net.

2.) I found a reply to an earlier request: Enzo Coviello mentions equivalence to a test for intercept=0 in a poisson model with offset term log(n_expected) (based on articles by Berry (1983) and a technical report by Therneau and Offord (1999)).

This is more tricky: I tried it and the resulting p-values are plausible. However one thing about them contradicts my intuition of this test:

As an approximation I can calculate a normal (two-sample) logrank-test for equality of the survivor function of my sample and of the population. This approximation should - in my opinion - overestimate the p-value (i.e. underestimate the value of the test-statistic), because it treats the population survivor function as a sample survivor function and thus introduces uncertainty that does not exist. So this approximation should be more conservative than the one-sample test.

However, when I follow Enzo Voviellos advice, I get p-values that are a little bit larger than that of the approximation. I find this disturbing as I think it should be the other way around. So I do not really trust the results.

Therefore I would like to know, if anyone can point me to a stata-implementation of this test.

Thanks in advance

Mark

Dr. Mark Trappmann

Universit�t Konstanz

Fachbereich Politik und Verwaltungswissenschaften

Fach D92

78457 Konstanz

Raum D306

Tel: 07531-88-2321

http://www.uni-konstanz.de/struktur/fuf/polfak/trappmann

*

* 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/

- Prev by Date:
**Re: st: compiling mata code** - Next by Date:
**st: Re: standard errors for 2SLS** - Previous by thread:
**st: Memory Problem/ Big Stata File** - Next by thread:
**st: using variable list instead of listing all variables?** - Index(es):

© Copyright 1996–2024 StataCorp LLC | Terms of use | Privacy | Contact us | What's new | Site index |