The LIFETEST procedure computes nonparametric estimates of the survival distribution function. You can request either the product-limit (Kaplan and Meier, 1958) or the life-table (actuarial) estimate of the distribution. Cox and Oakes (1984) and Kalbfleisch and Prentice (1980) provide good discussions of the product-limit estimator, and Lee (1992) and Elandt-Johnson and Johnson (1980) include detailed discussions of the life-table estimator. PROC LIFETEST computes nonparametric tests to compare the survival curves of two or more groups. The procedure also computes rank tests of association between the survival time variable and other concomitant variables, as given in Kalbfleisch and Prentice (1980, Chapter 6). For more information about PROC LIFETEST, see Chapter 56: The LIFETEST Procedure.