Uncertainty of measurement is defined as a “parameter, associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurand” (the measurand is the particular quantity subject to measurement) (International Vocabulary of Metrology, 2008).
There is growing recognition of the importance of Measurement Uncertainty (MU) and traceability to assuring the reliability of measurement. This is reflected in the standard ISO/IEC 17025:2005 and ISO 15189:2012, which contain enhanced requirements concerning these issues. The reactions to these developments range from interpretation at a minimal level, to implementation in a full and costly manner. Uncertainty of measurement is best estimated within the individual laboratory environment. All factors which will have a significant influence on the test or measurement result must be included in the estimated process. There must be suitable programs utilizing reference standards, instruments and materials to ensure on-going and adequate quality control and repeatability and reproducibility of methods and equipment over time. In many instances, it will be possible to utilize quality control data in assessing uncertainty components such as precision. Where these data are not available, it may be necessary to carry out precision studies or to rely on published information about the method or portions of it until the laboratory can obtain its own estimates. The ILAC-G17:2002 should be used as a guidance document as well to supplement the content of this document.