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Syntax: LIFETEST Procedure

The following statements are available in the LIFETEST procedure:

The simplest use of PROC LIFETEST is to request the nonparametric estimates of the survivor function for a sample of survival
times. In such a case, only the PROC LIFETEST statement and the TIME statement are required. You can use the STRATA statement
to divide the data into various strata. A separate survivor function is then estimated for each stratum, and tests of the
homogeneity of strata are performed. However, if the GROUP= option is also specified in the STRATA statement, stratified tests
are carried out to test the k samples that are defined by the GROUP= variable while controlling for the effect of the STRATA variables. You can specify
covariates in the TEST statement. PROC LIFETEST computes linear rank statistics to test the effects of these covariates on
survival.

The PROC LIFETEST statement invokes the procedure. All statements except the TIME statement are optional, and there is no
required order for the statements that follow the PROC LIFETEST statement. The TIME statement specifies the variables that
define the survival time and censoring indicator. The STRATA statement specifies a variable or set of variables that define
the strata for the analysis. The TEST statement specifies a list of numeric covariates to be tested for their association
with the response survival time. Each variable is tested individually, and a joint test statistic is also computed. The ID
statement provides a list of variables whose values identify observations in the product-limit, Breslow, or Fleming-Harrington
estimates. When only the TIME statement appears, no strata are defined and no tests of homogeneity are performed.