Decision Rule for Calibrations
Adhering to Our Standards
Quality Control Solutions, Inc. (QCSI), accredited to ISO/IEC 17025:2017, employs a “decision rule” to measure uncertainty (MU) for reporting numerical results as a “pass” or “fail” based on whether they fall within the specified limits. In the past, Statements of Conformity were referred to as Compliance Statements in the 2005 version of the Standard. However, the 2017 version of the Standard clearly articulates that such statements must consider the decision rule applied when reporting a result as a pass or fail.
Quality Control Solutions, Inc. offers two levels of calibration. Each level is defined as “Decision Rule” itemized by a specific number. The two options are as follows:
Decision Rule No. 1 (Default)
The calibration performed and results entered on the “Certificate of Calibration” includes the as found data, as left data and tolerances for each dataset. The tolerance is used in establishing the Risk Level.
Decision Rule No. 2 (Optional If Purchased)
The calibration performed and results entered on the “Certificate of Calibration” includes the as found data, as left data, tolerances and uncertainty for each dataset. The TUR and CMC, combined with the tolerance is used in establishing the Risk Level.
The rule to be applied must be agreed with the customer at the contract review stage and must be stated in the final report (if not inherent in the specification or standard against which the statement is made). Quality Control Solutions, Inc.’s standard rule utilized is Decision No. 1; however, Decision Rule No. 2 is available upon request, and at an increased rate.
Uncertainty of Measurement
Measurement Uncertainties are reported with a coverage factor k=2, providing a level of confidence of approximately 95%. All calibrations have been performed using processes that have a TUR (Test Uncertainty Ratio) of 4:1 or better (3:1 for mass calibrations), unless otherwise noted. CMC: Calibration Measurement Capability
Compliance with Specification
The Uncertainty of measurement has been taken into account when determining compliance with specification, as per ILAC-G8. If the expanded measurement uncertainty intervals center about one or more measured values were both in as well as out of specification (upper or lower), it is not possible to state compliance or non-compliance based on a 95% coverage probability for the expanded measurement uncertainty.
Risk Level Definitions
Pass – The measured value of the equipment was observed in specification at the points tested, Additionally, the expanded measurement uncertainty intervals about the measured values were in specification.
P‡ (Conditional Pass) – The measured values of the equipment were observed in specification at the points tested. However, a portion of the expanded measurement uncertainty intervals about one or more measured values exceeded specification. Consequently, compliance with specification cannot be declared based on the stated.
F‡ (Conditional Fail) – One or more measured values of the equipment were observed out of specification at the points tested. However, a portion of the expanded measurement uncertainty intervals about one or more measured values stated coverage probability.
Fail – One or more measured values of the equipment were observed out of specification at the points tested. Additionally, the expanded measurement uncertainty intervals about one or more measured values were entirely outside the specification.
TUR – Test Uncertainty Ratio
CMC – Calibration and Measurement Capability