Solution
= Solution
The <Bayesian network> has a shared parent $\psi$ and, for each hospital, the chain $\psi\to\theta_i\to y_i$. A plate encloses the hospital-specific pair. Observed counts are shaded; the local rates are <latent variables>. Conditional on $\psi$, the pairs are independent.
\Image[/past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2008/iii/paper-44-poisson-exponential-graph.png]
{title=Directed graph of a Poisson–exponential hierarchical model}