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From |
Steven Samuels <sjhsamuels@earthlink.net> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Kruskal-Wallis equivalent for survey data with pweight |

Date |
Sat, 1 Nov 2008 11:27:22 -0400 |

**************************CODE BEGINS************************** sysuse auto,clear svyset _n stset mpg sts test foreign, logrank svy: stcox foreign ***************************CODE ENDS*************************** -Steve

--You have not given us a good reason for preferring the K-W test. Itis the most widely known rank test for comparing >2 groups, butthere are many others. The test from -stcox- is appropriate forany positive random variable, censored or not. It has power todetect group differences even if the proportional-hazardsassumption is false. You report the p-value from the teststatistic, but you need not report estimated coefficients-thesedepend on the truth of the proportional-hazards assumption.Instead, plot the weighted survival or distribution curves.However, a k-sample test is rarely enough by itself, even if"significant". The real questions are: which groups differ fromone another? how do they differ? are the differences explained ormoderated by other factors?Good luck! Steve On Nov 1, 2008, at 7:12 AM, Aca N.T. wrote:Thanks Maarten & Steven, I have to change the analyses for LOS. However, I've picked a wrong example here since I have some other skewed variables for which KW test remains appropriate I think (eg.triglyceride level). Can you suggest how to perform the analysisusingStata? Thanks in advance. AcaOn Fri, Oct 31, 2008 at 4:24 PM, Maarten buis<maartenbuis@yahoo.co.uk> wrote:--- "Aca N.T." <acant29@gmail.com> wrote:I have a simple question about testing length of stay (LOS)differences among 5 groups. The response variable (LOS) has askeweddistribution. I have previously transformed the LOS (log transformation) and tried parametric statistic (ANOVA using svy:regress), but not happy when performing back-transformation for SD/SE. I rarely used non-parametric statistics before even fornon-survey data, so really this issue is a hassle for me. Ibelieve,however, that Stata has a test equivalent to Kruskal-Wallis for survey data.The conventional way of analysing length of stay data is usingsurvivalanalysis. So I would -stset- the data, and than use -sts test- to do the test. You can specify weights in the -stset- command. See: -help stset- and -help -sts test-. Hope this helps, Maarten ----------------------------------------- Maarten L. Buis Department of Social Research Methodology Vrije Universiteit Amsterdam Boelelaan 1081 1081 HV Amsterdam The Netherlands visiting address: Buitenveldertselaan 3 (Metropolitan), room N515 +31 20 5986715 http://home.fsw.vu.nl/m.buis/ ----------------------------------------- * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/* * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/* * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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**References**:**Re: st: Kruskal-Wallis equivalent for survey data with pweight***From:*"Aca N.T." <acant29@gmail.com>

**Re: st: Kruskal-Wallis equivalent for survey data with pweight***From:*Steven Samuels <sjhsamuels@earthlink.net>

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