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. The texts by Cox and Oakes (1984) and Kalbfleisch and Prentice (1980) provide good discussions of the product-limit estimator, and the texts by 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 of the survival time variable with other concomitant variables as given in Kalbfleisch and Prentice (1980, Chapter 6). For more information about PROC LIFETEST, see Chapter 52: The LIFETEST Procedure.