The LIFETEST Procedure

OUTSURV= Data Set

You can specify the OUTSURV= option in the PROC LIFETEST statement to create an output data set that contains the survival estimates. The data set contains the following columns:

  • any specified BY variables

  • a numeric variable STRATUM that numbers the strata, if you specify the STRATA statement

  • any specified STRATA variables, their values coming from either their original values or the midpoints of the stratum intervals if endpoints are used to define strata (semi-infinite intervals are labeled by their finite endpoint)

  • the GROUP= variables, if you specify the GROUP= option in the STRATA statement

  • the time variable as specified in the TIME statement. For METHOD=KM, METHOD=BRESLOW, or METHOD=FH, it contains the observed failure or censored times. For the life-table estimates, it contains the lower endpoints of the time intervals.

  • SURVIVAL, a variable that contains the survivor function estimates

  • CONFTYPE, a variable that contains the name of the transformation applied to the survival time in the computation of confidence intervals

  • SDF_LCL, a variable that contains the lower limits of the pointwise confidence intervals for the survivor function

  • SDF_UCL, a variable that contains the upper limits of the pointwise confidence intervals for the survivor function

If the estimation uses the product-limit, Breslow, or Fleming-Harrington method, then the data set also contains the following:

  • _CENSOR_, an indicator variable that has a value 1 for a censored observation and a value 0 for an event observation

  • SDF_STDERR, a variable that contains the standard error of the survivor function estimator

  • HW_LCL, a variable that contains the lower limits of the Hall-Wellner confidence bands (if you specify the CONFBAND=HW option or the CONFBAND=ALL option in the PROC LIFETEST statement)

  • HW_UCL, a variable that contains the upper limits of the Hall-Wellner confidence bands (if you specify the CONFBAND=HW option or the CONFBAND=ALL option in the PROC LIFETEST statement)

  • EP_LCL, a variable that contains the lower limits of the equal-precision confidence bands (if you specify the CONFBAND=EP option or the CONFBAND=ALL option in the PROC LIFETEST statement)

  • EP_UCL, a variable that contains the upper limits of the equal-precision confidence bands (if you specify the CONFBAND=EP option or the CONFBAND=ALL option in the PROC LIFETEST statement)

If the estimation uses the life-table method, then the data set also contains the following:

  • MIDPOINT, a variable that contains the value of the midpoint of the time interval

  • PDF, a variable that contains the density function estimates

  • PDF_LCL, a variable that contains the lower endpoints of the PDF confidence intervals

  • PDF_UCL, a variable that contains the upper endpoints of the PDF confidence intervals

  • HAZARD, a variable that contains the hazard estimates

  • HAZ_LCL, a variable that contains the lower endpoints of the hazard confidence intervals

  • HAZ_UCL, a variable that contains the upper endpoints of the hazard confidence intervals

Each survival function contains an initial observation with the value 1 for the SDF and the value 0 for the time. The output data set contains an observation for each distinct failure time if the product-limit, Breslow, or Fleming-Harrington method is used, or it contains an observation for each time interval if the life-table method is used. The product-limit, Breslow, or Fleming-Harrington survival estimates are defined to be right continuous; that is, the estimates at a given time include the factor for the failure events that occur at that time.