Dictionary · Quality & Accreditation
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.
Related terms
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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.
NIST SOP 30 / GLP 1
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
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
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).
ANSI/NCSL Z540.3
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)
Proficiency testing
Evaluation of participant performance against pre-established criteria by means of interlaboratory comparisons — an ISO/IEC 17025 requirement for demonstrating ongoing competence.
ISO/IEC 17043:2023