Dictionary · Quality & Accreditation
Test uncertainty ratio (TUR)
The ratio of the tolerance of the unit under test to the expanded uncertainty of the measurement process used to test it. A 4:1 TUR is the traditional benchmark; lower ratios call for guard banding or risk analysis (ANSI/NCSL Z540.3).
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A documented rule describing how measurement uncertainty is accounted for when stating conformity with a specified requirement — required by ISO/IEC 17025:2017 when a laboratory reports pass/fail.
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Interlaboratory comparison
Organization, performance, and evaluation of measurements on the same or similar items by two or more laboratories under predetermined conditions.
ISO/IEC 17043:2023
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Verification where the specified requirements are shown to be adequate for an intended use — demonstrating a procedure is fit for its purpose.
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Test accuracy ratio (TAR)
The legacy ratio of unit-under-test tolerance to the accuracy specification of the standard used. Superseded in rigorous work by the test uncertainty ratio, which accounts for the whole measurement process.
Industry practice