The LIFETEST Procedure - SAS

1 SAS/STAT User s GuideThe LIFETEST ProcedureThis document is an individual chapter fromSAS/STAT User s correct bibliographic citation for this manual is as follows: SAS Institute Inc. User s Guide. Cary, NC:SAS Institute User s GuideCopyright 2016, SAS Institute Inc., Cary, NC, USAAll Rights Reserved. Produced in the United States of a hard-copy book: No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or byany means, electronic, mechanical, photocopying, or otherwise, without the prior written permission of the publisher, SAS a web download or e-book.

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5 5207 Syntax: LIFETEST Procedure ..5215 PROC LIFETEST Statement ..5215BY Statement ..5226 FREQ Statement ..5226ID Statement ..5227 STRATA Statement ..5227 TEST Statement ..5232 TIME Statement ..5232 WEIGHT Statement ..5234 Details: LIFETEST Procedure ..5234 Missing Values ..5234 Computational Formulas ..5234 Breslow, Fleming-Harrington, and Kaplan-Meier Methods ..5234 Life-Table Method ..5238 Pointwise Confidence Limits in the OUTSURV= Data Set ..5239 Simultaneous Confidence Intervals for Kaplan-Meier Curves ..5241 Kernel-Smoothed Hazard Estimate.

6 5243 Comparison of Two or More Groups of Survival Data ..5245 Rank Tests for the Association of Survival Time with Covariates ..5249 Analysis of Competing-Risks Data ..5251 Computer Resources ..5254 Output Data Sets ..5255 OUTCIF= Data Set ..5255 OUTSURV= Data Set ..5256 OUTTEST= Data Set ..5258 Displayed Output ..5258 Plot Options Superseded by ODS Graphics ..5265 ODS Table Names ..5270 ODS Graphics ..5271 Modifying the Survival Plots ..5273 Examples: LIFETEST Procedure ..5274 Example : Product-Limit Estimates and Tests of Association ..5274 Example : Enhanced Survival Plot and Multiple-Comparison Adjustments.

7 5288 Example : Life-Table Estimates for Males with Angina Pectoris ..52935206 FChapter 71: The LIFETEST ProcedureExample : Nonparametric Analysis of Competing-Risks Data ..5300 References ..5307 Overview: LIFETEST ProcedureA common feature of lifetime or survival data is the presence of right-censored observations due either towithdrawal of experimental units or to termination of the experiment. For such observations, you know onlythat the lifetime exceeded a given value; the exact lifetime remains unknown. Such data cannot be analyzed byignoring the censored observations because, among other considerations, the longer-lived units are generallymore likely to be censored.

8 The analysis methodology must correctly use the censored observations inaddition to the uncensored that discuss the survival analysis methodology include Collett (1994), Cox and Oakes (1984);Kalbfleisch and Prentice (1980); Klein and Moeschberger (1997); Lawless (1982); Lee (1992). Usersinterested in the theory should consult Fleming and Harrington (1991); Andersen et al. (1992).Usually, a first step in the analysis of survival data is the estimation of the distribution of the survival times are often calledfailuretimes, andeventtimes are uncensored survival times.

9 The survivaldistribution function (SDF), also known as the survivor function, is used to describe the lifetimes of thepopulation of interest. The SDF evaluated attis the probability that an experimental unit from the populationwill have a lifetime that exceedst that is, > the survivor function andTis the lifetime of a randomly selected experimental unit. TheLIFETEST Procedure can be used to compute nonparametric estimates of the survivor function either bythe product-limit method (also called the Kaplan-Meier method) or by the life-table method (also called theactuarial method).

10 The life-table estimator is a grouped-data analog of the Kaplan-Meier estimator. Theprocedure can also compute the Breslow estimator or the Fleming-Harrington estimator, which are asymptoticequivalent alternatives to the Kaplan-Meier functions closely related to the SDF are the cumulative distribution function (CDF), the probabilitydensity function (PDF), and the hazard function. The CDF, , is defined as1 is theprobability that a lifetime does not exceedt. The PDF, , is defined as the derivative , andthe hazard function, , is defined If the life-table method is chosen, the estimatesof the probability density function can also be computed.