
LIFE TABLES & KAPLANMEIER ANALYSIS: NONPARAMETRIC SURVIVAL ANALYSIS
Overview
Life tables refers to a statistical procedure which generates duration (time to event) distributions for an entire dataset or separately for each level of a factor. As such it is a form of nonparametric survival analysis. The primary output is a life table in which the rows are researcherdefined time intervals and the columns have to do with counts, probabilities, and cumulative probabilities of the event of interest occurring during the given time interval.
KaplanMeier survival analysis (KMSA) is a method of generating tables and plots of survival or hazard functions for event history data (time to event data). Time to event data might include time to a report of symptomatic relief following a treatment or time to making a contribution following receipt of a fundraising appeal. KMSA is also a form of nonparametric survival analysis. That is, KMSA is a descriptive procedure for timetoevent variables for use when time is considered the only salient variable.
Life tables and KMSA are not preferred when the purpose is to investigate the effects of covariates on time to event. Rather, parametric survival analysis methods or Cox regression (both discussed in separate volumes of the Statistical Associates "Blue Book" series) are typically used. If covariates other than time are thought to be important in determining duration to outcome, results reported by KMSA will represent misleading averages, obscuring important differences in groups formed by the covariates (ex., men vs. women). However, even when covariates may be found to be important, KMSA may still be fruitful in exploratory stages of research.
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Below is the unformatted table of contents.
LIFE TABLES AND KAPLANMEIER ANALYSIS Table of Contents Overview 5 Life Tables 6 Key Terms and Concepts 6 Example 6 Variables 6 Life tables analysis in SPSS 7 The SPSS user interface 7 SPSS options 8 SPSS life tables output 9 The life table 9 Median survival time table 10 Overall comparisons table 10 Survival function plot 12 One minus survival plot 13 Density function plot 14 Hazard function plot 14 Assumptions of life tables analysis 15 Censored cases not different 15 Probabilities depend on time 15 KaplanMeier Analysis 15 Overview 15 Key Concepts and Terms 16 Example 16 Censored cases 16 Time variable 17 Status variable 18 Stratification variable 18 Factors and factor comparisons 18 The “Compare Factor” button 19 The overall comparisons table 19 Survival tables and plots 21 Survival table 21 Mean and median for survival time table 22 The quartiles/percentiles table 23 The survival plot 23 The “One minus survival functions” plot 24 Hazard plot 25 Log survival plot 26 Saving output as variables 27 Assumptions 28 Events dependent only on time 28 Frequently asked questions about KMSA 29 How do you obtain KMSA output in Stata? 29 How are KaplanMeier survival tables related to "Life Tables"? 30 Bibliography 30 Pagecount: 32