Uncertainty in measurement and total error – are they so incompatible?

Abstract

There appears to be a growing debate with regard to the use of "Westgard style" total error and "GUM style" uncertainty in measurement. Some may argue that the two approaches are irreconcilable. The recent appearance of an article "Quality goals at the crossroads: growing, going, or gone" on the well-regarded Westgard Internet site requires some comment. In particular, a number of assertions which relate to ISO 15189 and uncertainty in measurement appear misleading. An alternate view of the key issues raised by Westergard may serve to guide and enlighten others who may accept such statements at face value.

An approach for estimating measurement uncertainty in medical laboratories using data from long-term quality control and external quality assessment schemes

“…In contrast to the Guide to the Expression of Uncertainty in Measurement model (GUM) [7], which recommends the identification and elimination of bias at an early stage of the measurement process, the Westgard "total error approach" includes both an imprecision and bias component [8]. As discussed by Farrance et al [9], either procedure may be used to evaluate MU as ISO 15189 does not specify any particular approach. In either situation, however, the true value of the measurand cannot be known, as uncertainty associated with determining bias, in addition to assay imprecision, provide uncertainty as to the true value.…”

“…Depending on the test purpose, it might also be important to consider different models for calculating MU [4,9,10]. If the interpretation of a specific test result is largely provided by making a comparison with, e.g.…”

Sources of uncertainty in annual global horizontal irradiance data

“…GUM analyzes random and systematic errors separately (Farrance et al, 2016), and it calculates the uncertainty (u) only from random errors because it considers that systematic errors can be detected and corrected. For instance, site-adaptation techniques are applied to eliminate systematic errors in radiation databases (Polo et al, 2016), whereas systematic deviations in radiometers are mitigated using empirical correction factors.…”

Uncertainty in measurement and total error: different roads to the same quality destination?

“…In a recent opinion which focused directly on the TFG-TE summary [2], several potentially confusing statements regarding ISO15189 and the Evaluation of measurement data -Guide to the expression of uncertainty in measurement (usually referred to as the GUM) [3,4] were again promulgated in order to promote TE methods for assessing uncertainty in laboratory measurement. Even though we have tried to address some of these issues previously, the misunderstandings appear to continue [5]. In this opinion, we present an alternative view of the key issues in order to guide those who may accept all of the Westgard statements at face value.…”