Past exam of the mathematics course of the University of Cambridge / 2023 / iii / Paper 207 / 4 / d / ii / Solution

A residual $0.99$ must correspond to an event and fitted cumulative event count $0.01$. The event occurred much earlier than the model expected for that individual.

A residual $-4$ means that the fitted expected event count by the observed follow-up time exceeded the observed count by four. It may be a censored individual with fitted cumulative hazard four, or an individual whose event occurred only after fitted cumulative hazard five. In either case the individual remained event-free substantially longer than predicted.