Sample size required to detect difference in: | number per group | ||
---|---|---|---|

Age 16–19 | Age 20–24 | Age 25–30 | |

Uptake rate at α = 5% with 90% power, assuming true difference in uptake rate to be 50% of that observed in feasibility study | 1241 | 1024 | 145 |

Positive test rate at α = 5% with 90% power, assuming lower rate group to be 50% of higher rate group | 736 | 708 | 2122 |