The ICPHREG Procedure

Observations that contain a missing value for both the left boundary value and the right boundary value in the response are not used in the analysis. If a FREQ variable value is missing or 0, the observation is not used. If a STRATA variable is missing, the observation is not used unless you specify the MISSING option in the STRATA statement. If any explanatory variable that you specify in the MODEL statement has a missing value, that observation is not used in the model fitting. Predicted values, residuals, and regression diagnostics are computed for all observations that have no missing explanatory variable values.