Advisera’s ISO 17025 toolkit guides you through the implementation of ISO 17025. The ISO 17025 document template: Evaluation of Measurement Uncertainty Procedure and related Measurement Uncertainty Checklist and Measurement Uncertainty Record are available as part of the ISO 17025 toolkit; or as separate documents; to guide you in the process.
how can use uncertainty to evaluate the competence of the operators and also that the method is fit for purpose
A complete discussion of measurement uncertainty is outside of the scope of the toolkit. Measurement uncertainty is a statistical measure, offering a range within which there is an equal probability of the result value lying, at a particular confidence. This uncertainty estimate is a combination of all factors that affect the variability of results, on method basis; so cannot be used directly to evaluate the competence of personnel performing the method. One way of evaluating the competence of the operators, is to analyse the variation of groups of results during or after validation.
To state that a method is fit for its intended purpose, means providing evidence that the method is sufficiently reliable, so that the method can be used with confidence for a client to make a decision; based on results provided. The performance of a method must be evaluated through validation, along with an evaluation of measurement uncertainty. Uncertainty of measurement comprises many components, over a period of time for methods that have many variables. Depending on the purpose of the method a suitably small uncertainty may have to be achieved for a method to be fit for purpose. Look to regulatory or sector guidelines on acceptable or target uncertainties.