Dictionary · Quality & Accreditation
Check standard
A stable artifact or instrument measured regularly within a measurement assurance program; its control chart reveals drift, shifts, or loss of statistical control of the process.
Related terms
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Guard band
An interval applied between the tolerance limit and the acceptance limit to control the risk of false accept or false reject given measurement uncertainty — commonly the expanded uncertainty U, per ILAC-G8.
ILAC-G8:09/2019
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 Superseded in rigorous work by the test uncertainty ratio, which accounts for the whole measurement process.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
Decision rule
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.
ISO/IEC 17025:2017, 3.7
Process measurement assurance
A program of intermediate checks using check standards and control charts to demonstrate that a measurement process remains in statistical control between calibrations, as described in NIST SOP 30.
NIST SOP 30 (2019)
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
Calibration and measurement capability (CMC)
The smallest uncertainty of measurement a laboratory can achieve within its accredited scope when performing more or less routine calibrations of nearly ideal devices — the uncertainty published in its scope of accreditation.
ILAC-P14:09/2020