FA-100419 / Feature preprocessing fit scope / Member archive

Median and interquartile scaling applies fitted state incorrectly · case 04

Median and interquartile scaling applies fitted state incorrectly.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Use linear-interpolated quartiles at positions p*(n-1), median at p=.5, and scale by Q3-Q1. A zero IQR maps all values to zero. Round to six decimals.

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
quartile spread	`[-0.6, 0.0, 0.6]`	`[-1, 0, 1]`	Failed

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

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