FA-65279 / Epidemic compartment models / Member archive

Household secondary attack rate: index requirement · case 04

Households without any index case dilute the attack rate.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Each household is [size, index_cases, secondary]; skip households without an index case, without members at risk, or with more secondaries than at-risk members; pooled SAR = sum secondary / sum (size-index); per-size table sorted by size ascending; return [pooled rounded 6 or None, table].

Why this case matters

Compartmental epidemic calculations drive outbreak forecasts, vaccine targets and hospital planning; a single wrong flow, rate conversion or boundary silently changes every downstream number.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: no index household	`[0.333333, [[3, 1.0], [4, 0.142857]]]`	`[0.6, [[3, 1.0], [4, 0.333333]]]`	Failed

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