Effective January 1st, 2012, all ISO/IEC 17025:2005 calibration laboratories are required to begin reporting measurement uncertainties for each measurement result. Fox Valley Metrology - Thread Check Inc. prides itself on being one of, if not the only lab to offer this via automated software. This automation allows us to provide this service at no additional cost.
For calibration laboratories, ISO/IEC 17025:2005 (clause 220.127.116.11) requires that “if a statement of compliance with a specification is made, this shall identify which clauses of the specification are met or not met”.
When compliance with a specification is made it should be clear to the customer which coverage probability for the expanded uncertainty has been used. Unless otherwise noted, the coverage probability will be 95%.
An explanation of In Tolerance, Out of Tolerance, and Within Uncertainty:
(Case 1) In Tolerance: If the specification limit is not breached by the measurement result plus the expanded uncertainty with a 95% coverage probability, then compliance with the specification can be stated. This can be reported as “In Tolerance”.
(Case 4) Out of Tolerance: If the specification limit is exceeded by the measurement result minus the expanded uncertainty with a 95% coverage probability, then noncompliance with the specification can be stated. This can be reported as “Out of Tolerance”.
(Case 2 & 3) Within Uncertainty: If the measurement result plus/minus the expanded uncertainty with a 95 % coverage probability overlaps the limit, it is not possible to state compliance or non-compliance. The measurement result and the expanded uncertainty with a 95 % coverage probability should then be reported together with a statement indicating that neither compliance nor non-compliance was demonstrated. A suitable statement to cover these situations would be “Within Uncertainty”.