= Solution
Plot each observed <mortality> proportion vertically against its operation count horizontally, retaining the hospital labels. The required points, together with the target and approximate control bands used below, give the following <hospital mortality funnel plot>.
\Image[/past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2004/iii/paper-38-mortality-funnel.png]
{title=Hospital mortality proportions against operation counts with a 20% target and approximate pointwise 95% binomial control limits}
Hospitals sharing an operation count remain separate labeled points; equal observed <mortality> proportions at different volumes should not be treated as equally precise.
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