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Table 3 Calculations for the log-rank test to compare treatments for the data in Table 1

From: Statistics review 12: Survival analysis

Survival time (days) Treatment group Number known to be alive (ri) Deaths (di) Risk for death (di/ri) Number known to be alive from treatment group 2 (r2i) Expected number of events in treatment group 2 (E2i)
0       
1 2 15 2 2/15 = 0.133 8 8 × 0.133 = 1.07
1 2      
4 2 13 1 1/13 = 0.077 6 6 × 0.077 = 0.46
5 2 12 1 1/12 = 0.083 5 5 × 0.083 = 0.42
6+ 2 11 0 0/11 = 0 4 4 × 0 = 0.00
8 1 10 1 1/10 = 0.100 3 3 × 0.100 = 0.30
9 2 9 1 1/9 = 0.111 3 3 × 0.111 = 0.33
9+ 2 8 0 0/8 = 0 2 2 × 0 = 0.00
12 1 7 1 1/7 = 0.143 1 1 × 0.143 = 0.14
15+ 1 6 0 0/6 = 0 1 1 × 0 = 0.00
22 2 5 1 1/5 = 0.200 1 1 × 0.200 = 0.20
25+ 1 4 0 0/4 = 0 0 0 × 0 = 0.00
37 1 3 1 1/3 = 0.333 0 0 × 0 = 0.00
55 1 2 1 1/2 = 0.500 0 0 × 0 = 0.00
72+ 1      
       E2 = 2.92