FA-65509 / Ecological population dynamics / Member archive

Two-sample mark-recapture abundance: chapman numerator · case 04

Chapman estimates are biased low, especially with few recaptures.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Recaptures must be in [0, min(marked, caught)] else None; 'lp' = M*C/R ([None, None] when R=0, no variance); Chapman = (M+1)(C+1)/(R+1)-1 with variance (M+1)(C+1)(M-R)(C-R)/((R+1)^2 (R+2)); return [estimate rounded 2, variance rounded 2 or None].

Why this case matters

Population projections set harvest quotas, conservation status and pest-control timing; a wrong update order, boundary or rate conversion silently changes management advice.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: trout chapman	`[570.43, 10077.1]`	`[580.95, 10077.1]`	Failed

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