The LIFETEST Procedure

Displayed Output

Subsections:

The following sections describe the output that PROC LIFETEST produces by default. The output is organized into various tables, which are discussed in their order of appearance. The set of tables that PROC LIFETEST produces for a survival analysis, specifically with one type of failure, is different from the set of tables that it produces for an analysis of competing-risks data, which have multiple types of failure.

Tables for Survival Analysis

Product-Limit Survival Estimates

The "Product-Limit Survival Estimates" table is displayed if you request the product-limit method of estimation. The table displays the following:

  • the observed (event or censored) time

  • the number of units at risk (if you specify the ATRISK option in the PROC LIFETEST statement)

  • the number of events (if you specify the ATRISK option in the PROC LIFETEST statement)

  • the product-limit estimate of the survivor function

  • the corresponding estimate of the cumulative distribution function of the failure time

  • the standard error estimate of the survivor function estimator

  • the Nelson-Aalen cumulative hazard function estimate (if you specify the NELSON option in the PROC LIFETEST statement)

  • the standard error of the Nelson-Aalen estimator (if you specify the NELSON option in the PROC LIFETEST statement)

  • the number of event times that have been observed

  • the number of event or censored times that remain to be observed

  • the frequency of the observed times (if you specify the FREQ statement)

  • values of the ID variables (if you specify the ID statement)

The ODS name of this table is ProductLimitEstimates.

Breslow Survival Estimates

The "Breslow Survival Estimates" table is displayed if you request the Breslow method of estimation. The table displays the following:

  • the observed (event or censored) time

  • the number of units at risk (if you specify the ATRISK option in the PROC LIFETEST statement)

  • the number of events (if you specify the ATRISK option in the PROC LIFETEST statement)

  • the Breslow estimate of the survivor function

  • the corresponding estimate of the cumulative distribution function of the failure time

  • the standard error estimate of the survivor function estimator

  • the Nelson-Aalen cumulative hazard function estimate (if you specify the NELSON option in the PROC LIFETEST statement)

  • the standard error of the Nelson-Aalen estimator (if you specify the NELSON option in the PROC LIFETEST statement)

  • the number of event times that have been observed

  • the number of event or censored times that remain to be observed

  • the frequency of the observed times (if you specify the FREQ statement)

  • values of the ID variables (if you specify the ID statement)

The ODS name of this table is BreslowEstimates.

Fleming-Harrington Survival Estimates

The "Fleming-Harrington Survival Estimates" table is displayed if you request the Fleming-Harrington method of estimation. The table displays the following:

  • the observed (event or censored) time

  • the number of units at risk (if you specify the ATRISK option in the PROC LIFETEST statement)

  • the number of events (if you specify the ATRISK option in the PROC LIFETEST statement)

  • the Fleming-Harrington estimate of the survivor function

  • the corresponding estimate of the cumulative distribution function of the failure time

  • the standard error estimate of the survivor function estimator

  • the Nelson-Aalen cumulative hazard function estimate (if you specify the NELSON option in the PROC LIFETEST statement)

  • the standard error of the Nelson-Aalen estimator (if you specify the NELSON option in the PROC LIFETEST statement)

  • the number of event times that have been observed

  • the number of event or censored times that remain to be observed

  • the frequency of the observed times (if you specify the FREQ statement)

  • values of the ID variables (if you specify the ID statement)

The ODS name of this table is FlemingEstimates.

Quartile Estimates

The "Quartiles Estimates" table is displayed if you request the product-limit, Breslow, or Fleming-Harrington method of estimation. The table displays the following:

  • point estimates of the quartiles of the survival times

  • the lower and upper confidence limits for the quartiles

The ODS name of this table is Quartiles.

Mean Estimate

The "Mean Estimate" table is displayed if you request the product-limit, Breslow, or Fleming-Harrington method of estimation. The table displays the following:

  • the estimated mean survival time

  • the estimated standard error of the mean estimator

The ODS name of this table is Means.

Life-Table Survival Estimates

The "Life-Table Survival Estimates" table is displayed if you request the life-table method of estimation. The table displays the following:

  • the time intervals into which the failure and censored times are distributed. Each interval is from the lower limit, up to but not including the upper limit; if the upper limit is infinity, the missing value is printed.

  • the number of events that occur in the interval

  • the number of censored observations that fall into the interval

  • the effective sample size for the interval

  • the estimate of conditional probability of events (failures) in the interval

  • the standard error of the conditional probability estimator

  • the estimate of the survival function at the beginning of the interval

  • the estimate of the cumulative distribution function of the failure time at the beginning of the interval

  • the standard error estimate of the survivor function estimator

  • the estimate of the median residual lifetime, which is the amount of time elapsed before reducing the number of at-risk units to one-half. This is also known as the median future lifetime in Elandt-Johnson and Johnson (1980)).

  • the estimated standard error of the median residual lifetime estimator

  • the density function estimated at the midpoint of the interval

  • the standard error estimate of the density estimator

  • the hazard rate estimated at the midpoint of the interval

  • the standard error estimate of the hazard estimator

The ODS name of this table is LifetableEstimates.

Summary of the Number of Censored and Uncensored Values

The "Summary of the Number of Censored and Uncensored Values" table displays following:

  • the stratum identification (if you specify the STRATA statement)

  • the total number of observations

  • the number of event observations

  • the number of censored observations

  • the percentage of censored observations

The ODS name of this table is CensoredSummary.

Rank Statistics

The "Rank Statistics" table contains the test statistics of the nonparametric k-sample tests. The ODS name of this table is HomStats.

Covariance Matrix for the Log-Rank Statistics

The "Covariance Matrix for the Log-Rank Statistics" table is displayed if the log-rank k-sample test is requested. The ODS name of this table is LogrankHomCov.

Covariance Matrix for the Wilcoxon Statistics

The "Covariance Matrix for the Wilcoxon Statistics" table is displayed if the Wilcoxon k-sample test is requested. The ODS name of this table is WilHomCov.

Covariance Matrix for the Tarone Statistics

The "Covariance Matrix for the Tarone Statistics" table is displayed if the Tarone-Ware k-sample test is requested. The ODS name of this table is TaroneHomCov.

Covariance Matrix for the Peto Statistics

The "Covariance Matrix for the Peto Statistics" table is displayed if the Peto-Peto k-sample test is requested. The ODS name of this table is PetoHomCov.

Covariance Matrix for the ModPeto Statistics

The "Covariance Matrix for the ModPeto Statistics" table is displayed if the modified Peto-Peto k-sample test is requested. The ODS name of this table is ModPetoHomCov.

Covariance Matrix for the Fleming Statistics

The "Covariance Matrix for the Fleming Statistics" table is displayed if the Fleming-Harrington k-sample test is requested. The ODS name of this table is FlemingHomCov.

Test of Equality over Strata

The "Test of Equality over Strata" table is displayed if an unstratified k-sample test is carried out. The table contains the chi-square statistics, degrees of freedom, and p-values of the nonparametric tests and the likelihood ratio test (which is based on the exponential distribution). The ODS name of this table is HomTests.

Stratified Test of Equality over Group

The "Stratified Test of Equality over Group" table is displayed if a stratified test is carried out. The tables contains the chi-square statistics, degrees of freedom, and p-values of the stratified tests. The ODS name of this table is HomTests.

Scores for Trend Test

The "Scores for Trend Test" table is displayed if you specify the TREND option in the STRATA statement. The table contains the set of scores used to construct the trend tests. The ODS name of this table is TrendScores.

Trend Tests

The "Trend Tests" table is displayed if you specify the TREND option in the STRATA statement. The table contains the results of the trend tests. The ODS name of this table is TrendTests.

Adjustment for Multiple Comparisons for the Log-Rank Test

The "Adjustment for Multiple Comparisons for the Log-Rank Test" table is displayed if the log-rank test and a multiple-comparison adjustment method are specified. The table contains the chi-square statistics and the raw and adjusted p-values of the paired comparisons. The ODS name of this table is SurvDiff.

Adjustment for Multiple Comparisons for the Wilcoxon Test

The "Adjustment for Multiple Comparisons for the Wilcoxon Test" table is displayed if the Wilcoxon test and a multiple-comparison method are specified. The table contains the chi-square statistics and the raw and adjusted p-values of the paired comparisons. The ODS name of this table is SurvDiff.

Adjustment for Multiple Comparisons for the Tarone Test

The "Adjustment for Multiple Comparisons for the Tarone Test" table is displayed if the Tarone-Ware test and a multiple-comparison method are specified. The table contains the chi-square statistics and the raw and adjusted p-values of the paired comparisons. The ODS name of this table is SurvDiff.

Adjustment for Multiple Comparisons for the Peto Test

The "Adjustment for Multiple Comparisons for the Peto Test" table is displayed if the Peto-Peto test and a multiple-comparison method are specified. The table contains the chi-square statistics and the raw and adjusted p-values of the paired comparisons. The ODS name of this table is SurvDiff.

Adjustment for Multiple Comparisons for the ModPeto Test

The "Adjustment for Multiple Comparisons for the ModPeto Test" table is displayed if the modified Peto-Peto test and a multiple-comparison method are specified. The table contains the chi-square statistics and the raw and adjusted p-values of the paired comparisons. The ODS name of this table is SurvDiff.

Adjustment for Multiple Comparisons for the Fleming Test

The "Adjustment for Multiple Comparisons for the Fleming Test" table is displayed if the Fleming-Harrington test and a multiple-comparison method are specified. The table contains the chi-square statistics and the raw and adjusted p-values of the paired comparisons. The ODS name of this table is SurvDiff.

Univariate Chi-Squares for the Log-Rank Test

The "Univariate Chi-Squares for the Log-Rank Test" table is displayed if you specify the TEST statement. The table displays the log-rank test results for individual variables in the TEST statement. The ODS name of this table is LogUniChiSq.

Covariance Matrix of the Log-Rank Statistics

The "Covariance Matrix of the Log-Rank Statistics" table is displayed if you specify the TEST statement. The table displays the estimated covariance matrix of the log-rank statistics for association. The ODS name of this table is LogTestCov.

Forward Stepwise Sequence of Chi-Squares for the Log-Rank Test

The "Forward Stepwise Sequence of Chi-Squares for the Log-Rank Test" table is displayed if you specify the TEST statement. The table contains the sequence of partial chi-square statistics for the log-rank test in the order of the greatest increase to the overall test statistic, the degrees of freedom of the partial chi-square statistics, the approximate probability values of the partial chi-square statistics, the chi-square increments for including the given variables, and the probability values of the chi-square increments. The ODS name of this table is LogForStepSeq.

Univariate Chi-Squares for the Wilcoxon Test

The "Univariate Chi-Squares for the Wilcoxon Test" table displays the Wilcoxon test results for individual variables in the TEST statement. The ODS name of this table is WilUniChiSq.

Covariance Matrix of the Wilcoxon Statistics

The "Covariance Matrix of the Wilcoxon Statistics" table is displayed if you specify the TEST statement. The table displays the estimated covariance matrix of the Wilcoxon statistics for association. The ODS name of this table is WilTestCov.

Forward Stepwise Sequence of Chi-Squares for the Wilcoxon Test

The "Forward Stepwise Sequence of Chi-Squares for the Wilcoxon Test" table is displayed if you specify the TEST statement. The table contains the sequence of partial chi-square statistics for the Wilcoxon test in the order of the greatest increase to the overall test statistic, the degrees of freedom of the partial chi-square statistics, the approximate probability values of the partial chi-square statistics, the chi-square increments for including the given variables, and the probability values of the chi-square increments. The ODS name of this table is WilForStepSeq.

Tables for Competing-Risks Analysis

Summary of Failure Outcomes

The "Summary of Failure Outcomes" table displays the following:

  • the stratum identification, if you specify the STRATA statement

  • the group identification, if you specify the GROUP= option in the STRATA statement

  • the number of failure events of interest

  • the number of competing events

  • the number of censored observations

The ODS name of this table is FailureSummary.

Cumulative Incidence Function Estimates

The "Cumulative Incidence Function Estimates" table is displayed if you use the FAILCODE= option in the TIME statement to stipulate a competing-risk analysis. The table displays the following:

  • the group identification, if you specify the GROUP= option in the STRATA statement

  • the failure time of the event of interest

  • the estimated cumulative incidence function

  • the standard error estimate of the cumulative incidence estimator

  • the lower and upper confidence limits of the cumulative incidence function

The ODS name of this table is CIF.

Gray’s Test for Equality of Cumulative Incidence Functions

The "Gray’s Test for Equality of Cumulative Incidence Functions" table is displayed if you specify the STRATA statement. The table displays the following:

  • the failure code, if you specify more than one FAILCODE= option value

  • the chi-square statistic of Gray’s test (Gray 1988)

  • the degrees of freedom

  • the p-value

The ODS name of this table is GrayTest.