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Table 2 Calculations for the Kaplan–Meier estimate of the survival function for the treatment 2 data from Table 1

From: Statistics review 12: Survival analysis

Patient number Survival time (days) Number known to be alive (ri) Deaths (di) Proportion surviving (pi) Cumulative proportion surviving (S [t])
  0     1
1 1 8    
2 1 8 2 (8 - 2)/8 = 0.750 1 × 0.750 = 0.750
3 4 6 1 (6 - 1)/6 = 0.833 0.750 × 0.833 = 0.625
4 5 5 1 (5 - 1)/5 = 0.800 0.625 × 0.800 = 0.500
5 6+     
7 9 3 1 (3 - 1)/3 = 0.667 0.500 × 0.667 = 0.333
8 9+     
11 22 1 1 (1 - 1)/1 = 0.00 0.333 × 0.00 = 0.000