Table 3.
Approximate size of population and number of cases needed for 80% statistical power to be able to detect effectiveness of Program Xa
| # of controls/cases | 50% | 60% | 75% |
|---|---|---|---|
| If 70% of controls received Program X | |||
| 1 | 520,000 (156) | 287,000 (86) | 133,000 (40) |
| 2 | 384,000 (115) | 217,000 (65) | 100,000 (30) |
| 3 | 340,000 (102) | 193,000 (58) | 90,000 (27) |
| 4 | 317,000 (95) | 180,000 (54) | 83,000 (25) |
| 5 | 303,000 (91) | 173,000 (52) | 80,000 (24) |
| If 50% of controls received Program X | |||
| 1 | 473,000 (142) | 310,000 (93) | 150,000 (45) |
| 2 | 353,000 (106) | 230,000 (69) | 110,000 (33) |
| 3 | 310,000 (93) | 203,000 (61) | 93,000 (28) |
| 4 | 290,000 (87) | 187,000 (56) | 87,000 (26) |
| 5 | 277,000 (83) | 180,000 (54) | 83,000 (25) |
a
Assumes the annual incidence of inflicted traumatic brain injury in the population is 30/100,000. Numbers in parentheses are the number of cases needed