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From |
Tero T Kivela <tekivela@cc.helsinki.fi> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: sts test - which is better, A or B |

Date |
Tue, 18 May 2004 18:50:11 +0300 (EET DST) |

Dear Statalisters, Consider that one has a data set which can be divided into different classes based on cutpoints of certain variables - which ones and how does not matter here, but this can be done in two or more different ways. Say that one way of classifying results in four ordered categories which give the following result in -sts test-: Log-rank test for equality of survivor functions | Events Events stage1 | observed expected ------------+------------------------- 10 | 10 25.70 20 | 73 85.75 31 | 40 24.83 32 | 18 4.71 ------------+------------------------- Total | 141 141.00 Test for trend of survivor functions chi2(1) = 38.2276 Pr>chi2 = 0.0000 Test for trend of survivor functions The alternative way gives: Log-rank test for equality of survivor functions | Events Events stage2 | observed expected ----------+------------------------- 10 | 4 11.05 20 | 58 84.43 31 | 60 41.15 32 | 20 5.37 ----------+------------------------- Total | 142 142.00 Test for trend of survivor functions chi2(1) = 36.8827 Pr>chi2 = 0.0000 Intuitively, the classification which gives chi2(1) = 38.2276 divides the cases better accoridng to survival than the one which gives chi2(1) = 36.8827 There must be a way to test, statistically, whether orr not it is likely that the difference in chi-square has occurred by chance (as it may have in this example, unlike would be the case intuitively had the chi-square values been, say, 38.2 and 48.2. And: in this case, both classifications had four categories. What about comparsion of a classification which has three categories to one that has four categories. What would be the method to test for the difference between two Kaplan-Meier analyses. I have not seen any problems like this in a number of manuals on survival analysis. Best regards, T Kivela * * 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/

**Follow-Ups**:**Re: st: sts test - which is better, A or B***From:*Ronán Conroy <rconroy@rcsi.ie>

**st: Time taken for reshape command***From:*"Subhankar Nayak" <nayak@bellsouth.net>

**References**:**st: RE: RE: Poisson estimators for space time series in Stata***From:*Chandy C John <chandy.john@case.edu>

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