 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2006/iii/paper-45/2/d/solution

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

Summing the transmission table by its rows and columns gives

allele 2 allele 1 transmitted 5941 not transmitted 4951

Thus the marginal case-versus-pseudo-control odds ratio is

OR = \frac{59/41}{49/51} = \frac{3009}{2009} ≃ 1.498.

This is the requested approximate allelic effect. Keeping the parent-specific matching instead gives the discordant-pair odds ratio

c / b = 30/20 = 1.5

, numerically close here. Neither calculation makes the within-family allele observations independent population samples.

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