IBM SPSS COMPLEX SAMPLES 19 Complex Samples Cox Regression

Chapter

Complex Samples Cox Regression

The Complex Samples Cox Regression procedure performs survival analysis for samples drawn

by complex sampling methods.

A government law enforcement agency is concerned about recidivismrates in their area of

jurisdiction. One of the measures of recidivism is the time until second arrest for offenders. The

agency would like to model time to rearrest using Cox Regression on a sample drawn by complex

sampling methods, but they are worried the proportional hazards assumption is invalid across

age categories.

Persons released from their ﬁrstarrestduringthemonthofJune2003wereselectedfrom

sampled departments, and their case history inspected throughthe end of June 2006. The

sample is collected in recidivism_cs_sample.sav. The sampling plan used is contained in

recidivism_cs.csplan;because it makes use of a probability-proportional-to-size (PPS) method,

there is also a ﬁle containing thejoint selection probabilities (recidivism_cs_jointprob.sav). For

more information, see the topicSample Files in Appendix A in IBM SPSS Complex Samples

19.Use Complex Samples Cox Regressionto assess the validity of the proportional hazards

assumption and ﬁt a model with time-dependentpredictors, if appropriate.

The dataset contains the dates of release fromﬁr starr est and second arrest; since Cox regression

analyzes survival times, youneed to compute the amount of time between these dates.

However,Date of second arrest [date2] contains cases with the value 10/03/1582 , a missing

value for date variables. These are people who have not had a second offense, and we deﬁnitely

want to include them as right-censored cases in the model. The end of the follow-up period was

June 30, 2006, so we are going to recode 10/03/1582to 06/30/2006.

ETorecode these values, from the menus choose:

Transform> Compute Variable...