FA-100404 / Feature preprocessing fit scope / Member archive

Median imputation uses held-out rows while fitting · case 04

Median imputation uses held-out rows while fitting.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Train and values are scalar numeric lists with optional None. Fit the ordinary median, averaging the two middle observations for even size; use zero if no observations.

Why this case matters

A small deterministic preprocessing contract makes the fit boundary and transform behavior directly inspectable.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
odd training	`[4, 4]`	`[5, 4]`	Failed

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