The <Nelson–Aalen estimator> is
$$
\widehat H(t)=\sum_{t_j\leq t}\frac{d_j}{r_j}.
$$
For tied events, $d_j/r_j$ uses the number of events sharing time $t_j$ and the risk-set size just before that time.

At month 5,
$$
\widehat H_A(5)=\frac15+\frac14+1=\frac{29}{20},
\qquad
\widehat H_B(5)=\frac24=\frac12.
$$
Their ratio is $29/10=2.9$.

Solution

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

 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2022/iii/paper-207/4/c/solution