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Incoming links: Hospital mortality funnel plot
Past exam of the mathematics course of the University of Cambridge 2004 iii Paper 38 5 a Solution Created 2026-10-03 Updated 2026-10-14
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.
Past exam of the mathematics course of the University of Cambridge 2004 iii Paper 38 5 d Solution Created 2026-10-03 Updated 2026-10-14
Four advantages of the hospital mortality funnel plot are:
- It presents mortality and case volume together, making the difference in precision between small and large hospitals visible.
- Its volume-dependent control limits distinguish expected sampling scatter from observations deserving investigation, avoiding an indiscriminate ranking of raw rates.
- It displays all hospitals on one interpretable scale with a common target and identifies unusually low as well as unusually high rates.
- It makes the benchmark and statistical assumptions explicit and supports direct comparison as volumes change, without estimating the benchmark from potentially anomalous observations.
It does not automatically adjust for patient severity, referral patterns or data quality, and an outlying point does not establish a causal explanation.