FA-13010 / Numerical aggregation / Member archive

Merge central moment 4: The count polynomial uses the square of the count difference. · 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 1	`[3, "4", "26", "36", "146"]`	`[3, "4", "26", "36", "338"]`	Failed

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