Uncertainties
Introduction
The laboratory should have a procedure to estimate the uncertainty of test results. For uncertainty estimation the laboratory should identify all the components of uncertainty. Sources contributing to the uncertainty can include the reference materials used, the methods and equipment used for sampling and testing, environmental conditions and personnel.
Process for Quantifying of Uncertainty
The procedure to quantify uncertainty should be established as a part of reporting. Estimation of method‘s or result uncertainty depends on the data available about the method performance. The stages involved in developing the procedure are:
- Reconcile the information available within the existing data
- Identify sources of uncertainty
- Quantify individual uncertainties
- Build the model
- Use the uncertainty for reporting
For more information about the module Uncertainties and for screenshots go to this section.
Advantages of Uncertainty Evaluation
According to European co-operation for Accreditation: EA guidelines EA-4/16 on the expression of uncertainty in quantitative testing, advantages of uncertainty evaluation for testing laboratories are as follows:
- Measurement uncertainty assists in a quantitative manner in important issues such as risk control and the credibility of test results
- A statement of measurement uncertainty can represent a direct competitive advantage by adding value and meaning to the result
- The knowledge of quantitative effects of single quantities on the test result improves the reliability of the test procedure. Corrective measures may be implemented more efficiently and hence become more cost-effective
- The evaluation of measurement uncertainty provides starting points for optimizing the test procedures through a better understanding of the test process
- Clients such as product certification bodies need information on the uncertainty associated with results when stating compliance with specifications
- Calibration costs can be reduced if it can be shown from the evaluation that particular influence quantities do not substantially contribute to the uncertainty.
Related Documents
ISO 17025:2005, chapter 5.4.6
EURACHEM/CITAC Guide* Quantifying Uncertainty in Analytical Measurement, 2nd edition, QUAM:2000.1 http://www.eurachem.org
