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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