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Population standardization applies fitted state incorrectly · case 02

Population standardization applies fitted state incorrectly.

Member previewVariant 2 · 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	`[0.0, 1.414214]`	`[0, 2]`	Failed

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