CalculationConformity with Measurement Uncertainty
Conformity with Measurement Uncertainty
Compares the full measurement uncertainty interval against specification limits.
How to use the result
Agree this three-stage rule with guard band U before inspection. Other contractual or normative decision rules are not covered automatically.
Contact with a specification limit from outside remains indeterminate. Limits are inclusive for intervals contained completely within them.
The interval provides no absolute guarantee and no calculated risk of an incorrect decision. The coverage factor and uncertainty budget must be appropriate for the measurement.
Formulas
measurement interval = [y − U; y + U]acceptance interval = [LSL + U; USL − U], provided that LSL + U ≤ USL − UConforming: measurement interval entirely inside; nonconforming: entirely outside; otherwise indeterminate. Sources: ILAC-G8:09/2019, Guidelines on Decision Rules and Statements of Conformity: https://ilac.org/publications-and-resources/ilac-guidance-series/; JCGM 106:2012, guarded acceptance: https://www.bipm.org/documents/20126/2071204/JCGM_106_2012_E.pdf/fe9537d2-e7d7-e146-5abb-2649c3450b25