Definition and assessment of sampling and analytical accuracy.

Two independent definitions for quantifying measurement accuracy and two limiting schemes for their assessment are examined in this paper. Gauss' mean square error MSE is compared to the symmetric-range accuracy A, describing the range of measurements about a measurand. Both measures of accuracy account for systematic error (bias) and imprecision so as to quantify the closeness of estimates to the actual values being measured. Remarkably, it is found that the accuracy functions are closely equivalent for most method applications. Furthermore, details are presented on how to compute confidence limits on measurement accuracy so as to account for error in method evaluation. The confidence limits are qualitatively different in the case that the method undergoes extensive initial evaluation in comparison to a continual re-evaluation at each method application. To this end the statistical theories of tolerance as well as more familiar types of confidence intervals are applied.