A value close to a requirement boundary deserves a clear interpretation method. The decision should not depend on whichever reading of uncertainty produces the preferred outcome.
ILAC's 2019 guidance discusses decision rules for statements of conformity involving measurement uncertainty. ILAC — Decision Rules and Statements of Conformity (2019).
Establish the rule
For a test or dimensional requirement, identify the applicable decision rule before interpreting the result. Use the relevant standard, contract or competent assessment basis rather than inventing a universal approach.
Preserve the conclusion's scope
Record the result and the rule supporting the statement. Different decision rules can address different risks and contexts. A simple pass label without its basis may leave an important question unanswered, especially when the reported value lies near the boundary.
Source reviewed 25 October 2026. Interpretation and original diagrams: PLUSHIP / Qunhe. Examples are illustrative.
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