FA-13142 / Numerical aggregation / Member archive

Frequency central scatter: Uncentered second moments replace centered scatter. · case 02

The reduction disagrees with its explicit aggregation oracle.

Member previewVariant 2 · 3 implementations · 9 checks per implementation

Case contract

Rows [integer value, nonnegative frequency] represent replicated observations. Return unnormalised sum of squared deviations from their exact replicated mean as a Fraction string; zero total frequency returns None.

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	`"20"`	`"36/5"`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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