Table 1 Number of necessary events and sample size to obtain 80% statistical power
Scenario | Necessary number in two group | ||||
|---|---|---|---|---|---|
5-year Disease Free Survival | |||||
Unexposed group | Exposed group | Difference between exposed to unexposed | Hazard Ratio of exposed to unexposed | events | sample size |
90% | 95% | 5% | 0.49 | 67 | 550 |
85% | 80% | 5% | 0.65 | 173 | 862 |
80% | 85% | 5% | 0.73 | 318 | 790 |
75% | 80% | 5% | 0.78 | 491 | 1152 |
70% | 75% | 5% | 0.81 | 684 | 1646 |
65% | 70% | 5% | 0.83 | 884 | 1842 |
60% | 65% | 5% | 0.84 | 1084 | 2002 |