Past exam of the mathematics course of the University of Cambridge / 2022 / iii / Paper 207 / 4 / d / Solution

The three estimates are $9/4=2.25$, $3$, and $2.9$. They use different weightings of follow-up time and event times, but all indicate a substantially greater mortality hazard under Treatment A; the exponential and Nelson–Aalen estimates are particularly close.