FA-13675 / Numerical aggregation / Member archive

Contingency pearson reduction: Cells with zero observed count are excluded despite positive expectation. · case 05

The reduction disagrees with its explicit aggregation oracle.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

For a rectangular nonnegative integer count table, return the Pearson sum of (observed-expected)^2/expected under independence, with expected=row marginal*column marginal/grand total. Zero expected cells contribute zero; empty or zero-total tables return "0". Exact Fraction string; no inferential p-value claim.

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	`"4"`	`"8"`	Failed

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