FA-100364 / Feature preprocessing fit scope / Member archive

Population standardization uses held-out rows while fitting · case 04

Population standardization uses held-out rows while fitting.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Fit population mean and population standard deviation on nonempty train; transform values as z scores rounded to six decimals. A zero fitted deviation maps values to zero.

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
population scale	`[-1.0, 1.0]`	`[0, 2]`	Failed

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