FA-13005 / Numerical aggregation / Member archive

Merge central moment 4: Fourth-moment translation omits third-moment coupling. · case 05

The reduction disagrees with its explicit aggregation oracle.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Merge disjoint integer observation blocks into [count, exact mean, unnormalised central moments through order 4]. Empty blocks are identities; moments are Fraction strings, empty summary is zero.

Why this case matters

Exact bounded examples isolate a reduction defect without floating-point or external-service effects.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression 6	`[5, "16/5", "524/5", "-3348/25", "448772/125"]`	`[5, "16/5", "524/5", "-3348/25", "506372/125"]`	Failed

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