 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2009/iii/paper-41/2/b/i/solution

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

The observed positive counts are

200 (0.18) = 36

and

400 (0.08) = 32

. Thus the responder-only estimate is

p_{R} = \frac{36 + 32}{600} = \frac{68}{600} ≃ 11.33%.

This estimates the proportion among the responders; it does not yet address either kind of nonresponse.

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