Understanding measurement uncertainty in certified reference materials.

No measurement can be made with 100 percent accuracy.

There is always a degree of uncertainty, but for any important measurement, it’s essential to identify every source of uncertainty and to quantify the uncertainty introduced by each source.

In every field of commerce and industry, buyers require certified measurements to give them assurances of the quality of goods supplied: the tensile strength of steel; the purity of a drug; the heating power of natural gas, for example.

Suppliers rely on test laboratories, either their own or third parties, to perform the analysis or measurement necessary to provide these assurances. Those laboratories in turn rely on the accuracy and precision of their test instruments, the composition of reference materials, and the rigour of their procedures, to deliver reliable and accurate measurements.

Every stage of the process, every measurement device used introduces some uncertainty. Identifying and quantifying each source of uncertainty in order to present a test result with a statement quantifying the uncertainty associated with the result can be challenging. But no measurement is complete unless it is accompanied by such a statement.

This white paper will provide an overview of sources of measurement uncertainty relating to the manufacture and use of certified reference gases. It will explain how uncertainty reported with a test result can be calculated and it will explain the important differences between uncertainty, accuracy and precision.