FA-13380 / Numerical aggregation / Member archive

Empirical distinct draw collision: Only the largest category contributes collision pairs. · case 05

The reduction disagrees with its explicit aggregation oracle.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Return probability that two distinct uniformly chosen observation indices carry equal integer labels, as an exact Fraction string. Fewer than two observations returns None. Labels themselves are nominal; repeated indices are excluded.

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	`"1/5"`	`"4/15"`	Failed

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

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