Public evidence

engineering.measurement.cochran

Machine-checked verification for calculation version 1.0.0 · tier engine_tested

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Verification

9/9 calculation tests · Production surface contract 4/4

Golden tests 0 / 0
Boundary tests 6 / 6
Property tests 3 / 3
Production surface contract 4 / 4
Engine tested Yes
Source checked Yes
Artifact integrity PASS
Production attestation Embedded snapshot: unpublished · Build schema 1.0.0 ready · Semantic contract ✓ · Attestation report not published on origin · Live production status STALE (5 capabilities; 152 remain CURRENT) @ 2026-09-16T02:55:45.575Z
Semantic contract PASS
Evidence attested at 2026-09-14T00:43:05.498Z
Last production check 2026-09-14T00:43:05.498Z
Public / cache —
Origin —
Supplemental domain review Not performed
Named expert review Not performed

release artifacts aligned PASS
schema valid input executes PASS
engine success output validates schema PASS
schema rejects incomplete input PASS

Fingerprint sha256:a2f052d317354a8445116f83db295918471d140482da7c1858d596fae86f0577

Input schema sha256:5002f38c117712a48a9de76599e4d9890cf3171eb7c59b0438ce12b96d629b39 · Output schema sha256:a457b8d5978d22bd3d5cc7a1fed8e64b731c7598b691339218cd768c1cea6fff · Build-time SHA-256 digests prove published artifacts agree with each other (release_integrity.scope=workspace). Production attestation GETs canonical URLs twice (public/cached view and origin), including Capability HTML, via npm run attest:production --write (published at /.well-known/calculatorx-production-attestation.json) and fails if the public Capability page advertises a different calculation_version. This is artifact consistency, not an independent immutable release log.

Build & scope

Engine identity and declared limitations.

Tool: cochran
Engine: cochran
Engine build: 2026-09-16
Evidence core: 2026-09-16T01:30:16.780Z
Rendered: 2026-09-16T03:19:09.590Z
Last reviewed: —

Assumptions

ISO 5725-2 Cochran C = s_max² / Σ s_i² from k≥2 stated laboratory sample standard deviations. k=1 is rejected.
s_i ≥ 0. All-zero s is rejected (Σ s² must be > 0).
Not pooled s_p, not Hartley's F_max, and not a tabulated Ccrit pass/fail.

Limitations

Takes stated laboratory s_i — not a sample of observations
k=1 is rejected so this cannot wrap identity C=1
All-zero s is rejected (Σ s² must be > 0)
Does not compare C to a tabulated Ccrit(p, n, α)
Not pooled s_p and not Hartley's F_max

Sources

Standards and references supporting this tool specification. Methods are listed separately — they are algorithms, not bibliographic sources.

ISO 5725-2 — Repeatability and reproducibility of standard measurement methods — Cochran's C test
Supports: C = s_max² / Σ s_i² is the test statistic for an unusually large laboratory repeatability variance. Critical values depend on p, n, and α and are not applied here.
ISO 5725-1 — Accuracy (trueness and precision) of measurement methods and results — Repeatability standard deviation s_r
Supports: This page takes already-stated laboratory s_i. It does not estimate s_r from a collaborative-study table.

Published checks

Golden, boundary, and property cases included in this evidence build.

ID	Kind	Status	Detail
`boundary-coch`	boundary	pass	Expected C=0.5 · s_max=5 · k=3 · Actual C=0.5 · s_max=5 · k=3
`boundary-coch-equal`	boundary	pass	Expected C=0.5 · Actual C=0.5 · s_max=5 · k=2
`boundary-coch-zero-one`	boundary	pass	Expected C=1 · Actual C=1 · s_max=5 · k=2
`boundary-coch-one`	boundary	pass	Expected VALUE_OUT_OF_RANGE · Actual VALUE_OUT_OF_RANGE
`boundary-coch-allzero`	boundary	pass	Expected VALUE_MUST_BE_POSITIVE · Actual VALUE_MUST_BE_POSITIVE
`boundary-coch-missing`	boundary	pass	Expected MISSING_REQUIRED_INPUT · Actual MISSING_REQUIRED_INPUT
`property-coch`	property	pass	0.5
`property-coch-equal`	property	pass	0.5
`property-coch-alias`	property	pass	0.5