Projects

Measurement uncertainty activities 2006-2007

Activities in the area of measurement uncertainty supported by the NMS Chemical and Biological Metrology programme have involved:

Collaboration with ISO

Eurachem Measurement Uncertainty and Traceability working group

Collaboration with ISO

One of the principal activities supported by the NMS Chemical and Biological Metrology programme is the development of ISO TS 21748 into a full international Standard.  ISO TS 21748 provides detailed guidance on the use of collaborative study data in uncertainty estimation. This makes the process of uncertainty estimation considerably simpler for laboratories using published standard methods.

LGC is also providing support in the preparation of ISO TC69 - Application of statistical methods policy on software in statistical standards.  In addition LGC is contributing to work supporting guidance for six-sigma practitioners. Six-sigma is a collection of tools for process and quality improvement. LGC is providing a case study of fractional factorial designs in analytical method development.

Eurachem Measurement Uncertainty and Traceability working group

The Eurachem Measurement Uncertainty and Traceability working group has been responsible for the production of several publications which are available for download from the Eurachem website.  Measurement uncertainty and traceability are key quality issues, experts in the fields from LGC have been actively involved with this group since its formation.

During 2007 group completed of new guidance on "Use of uncertainty information in compliance assessment" which can be obtained from the Eurachem website.   The document extends existing minimal guidance by providing a framework for decision making given measurement results with uncertainty. The guidance stresses the importance of developing clear decision rules, from which unambiguous acceptance or rejection can be decided.  In addition, the text includes authoritative guidance on the reporting and interpretation of uncertainty when the uncertainty is proportional to the value of the measurand.  In such cases the uncertainty intervals generally become asymmetric.  The guide includes a discussion and general recommendations, followed by more detailed instructions on establishing rules for interpretation and by several examples.  The issue of compliance assessment has caused serious controversy in the sports doping field, and the new guidance will help to dispel some of the confusion in the area.

Another guidance document "Measurement uncertainty arising from sampling: A guide to methods and approaches" has also been finalised and is available on the Eurachem website.  Sampling is one of the major contributors to uncertainty in measurement, often being the dominant source of uncertainty for measurements on bulk materials.  The NMS Chemical and Biological Metrology programme provided support for a UK chairman of the working group and for development of drafts.  The text provides a variety of methods for assessing uncertainty in sampling, together with guidance on the relative merits and costs of each. Simple approaches suitable for routine use are included. 

Further information on any of the material above may be obtained by contacting the NMS helpdesk at LGC.