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Revenue outlier capping: The cap reads one rank too high · case 05

The cap sits one order statistic above the requested percentile.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

The cap is the nearest-rank pct-th percentile of the pooled values of both arms: sorted pooled value at 1-based rank ceil(pct/100 * N), clamped to [1, N]. Every value is capped (not dropped) at that threshold and each arm mean is taken over all its users. Empty arm -> None. Return [cap, capped control mean, capped treatment mean].

Why this case matters

Capping whales keeps revenue metrics sensitive; a per-arm cap biases the comparison itself.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
cap comes from pooled data	`[300, 78.75, 82.5]`	`[20, 8.75, 12.5]`	Failed

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