engineering.uncertainty.welch_satterthwaite

• Golden tests 0 / 0
• Boundary tests 6 / 6
• Property tests 4 / 4
• Production surface contract 4 / 4
}
• Engine tested Yes
• Source checked Yes
• Artifact integrity PASS
• Production attestation Embedded snapshot: STALE · Last attested schema matched 1.0.0 snapshot / local build · Semantic contract ✓ · Last attestation PASS · current evidence changed · re-attestation required · Public/cache ✓ · Origin ✓ · Live production status PASS (0 stale; 164 CURRENT) @ 2026-09-16T06:44:24.909Z
• Semantic contract PASS
• Evidence attested at 2026-09-16T06:44:24.203Z
• Last production check 2026-09-16T06:44:24.203Z
• Public / cache PASS
• Origin PASS
• 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:d609c74a6215dbd2f95f8c688ec955a44fb1b1722e4990703a23d2858b3d5ea7

Input schema sha256:eac919d25af450aeab502496247f636d0654dd754cee4037898e741cba00d856 · Output schema sha256:91c22db74bd4b74afc6434847efcfa44328831d784e03c1253897753af369b9c · 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.

Tool

welch-satterthwaite

Engine

welch-satterthwaite

Engine build

2026-09-15

Evidence core

2026-09-15T07:59:57.695Z

Rendered

2026-09-16T22:03:43.734Z

Last reviewed

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Assumptions

• JCGM 100:2008 G.4 Welch–Satterthwaite
• If uc omitted, u_c = RSS of uncorrelated u_i
• Infinite ν_i contribute 0 to the sum
• Not GUM model combination and not expanded U = k·u_c

Limitations

• Does not combine a measurement model (use Uncertainty propagate)
• Does not look up coverage factor k from a t-table
• Does not compute expanded U = k·u_c
• Uncorrelated RSS only when uc is omitted