75
Survival Probability Estimates
                          Survival Probabilities 
Yr  Combined       Each Year              Cumulative
1  On study 300
       Died 151
  Surviving 149  149/300 = 49.67%                 49.67%
2  On study 104
       Died  49
  Surviving  55   55/104 = 52.88%   .4967*.5288 = 26.27%
3  On study  30  
       Died  13 
  Surviving  17   17/ 30 = 56.67%   .2627*.5667 = 14.88%