OPTIONS LS=75 PS=50;

DATA a;

INFILE 'vasectmy.dat';

 INPUT PairNo Vasectmy Obesity Smoking MI;
 
 time = PairNo/4;
 
 CloneNo = PairNo*10000+Obesity*100+Smoking;
 
PROC PHREG;
  MODEL time*MI(0) = Vasectmy;
  STRATA CloneNo;

PROC PHREG;
  MODEL time*MI(0) = Vasectmy;
  STRATA PairNo;
 
PROC PHREG;
  MODEL time*MI(0) = Vasectmy Smoking;
  STRATA PairNo;
 
PROC PHREG;
  MODEL time*MI(0) = Vasectmy Obesity;
  STRATA PairNo;
  
PROC PHREG;
  MODEL time*MI(0) = Vasectmy Smoking Obesity;
  STRATA PairNo;
 
PROC PHREG;
  MODEL time*MI(0) = Vasectmy Smoking Obesity;
  
RUN: