The ICLIFETEST Procedure

Observations that have a missing value for both the left boundary and the right boundary are not used in the analysis. If a STRATA or FREQ variable value is missing, the observation is not used. However, you can treat missing values as an independent stratum if you specify the MISSING option in the PROC ICLIFETEST statement. If any variable that you specify in the TEST statement has a missing value, that observation is not used in the calculation of test statistics unless you specify the MISSING option in the PROC ICLIFETEST statement.