On the Stability Assessment of Reference Materials

As well as presenting comparative characteristics of domestic and international approaches to assessing the instability of reference materials, the paper describes proposed changes in R 50.2.031–2003. A proposed mathematical apparatus is based on an algorithm of actions for estimating the standard uncertainty from instability and the validity period of a reference material (RM). Approaches to estimating uncertainty from instability in cases of the absence or presence of a significant trend in a RM’s certified characteristic over time are considered. The minimum number of measurements necessary to study the stability of an RM is determined and justified. Smoothing of measurement results when assessing the stability of an RM is shown to lead to an overestimation of the period of validity.