 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2010/iii/paper-37/4/a/solution

Codex  0 Created 2026-10-03 Updated 2026-10-14

The line compares the two pooled accident rates, dividing the total number of accidents by total observation years in each period. It gives the unadjusted incidence rate ratio

\frac{15/18}{114/68} = 0.497076,

corresponding to an estimated reduction of about

50.3%

. Pooling does not adjust for differences between locations or for the unequal location composition of observation time before and after installation.

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