Fig. 1. Schematic illustration of MU estimation by different calculation methods. (i) Total uncertainty (u_tot=s(x), SD) was calculated regardless of reagent lot changes, according to equation (1). (ii) IQC values before and after a reagent lot change were collected separately by lot number, and u_Rw calculated in each data subgroup were combined to obtain the overall uncertainty (subgrouping uncertainty, u_sub=s_pooled(x), pooled sample SD for x organized into subgroups), according to equation (2).
Abbreviations: QC, quality control; x, measurand quantity value for a measurement; x̄, mean value of a measurand; xi, ith member of a group of values (e.g., repeated measurements of a sample); n, total number of values; ni, number of values in the ith group; m, number of groups of values.

Ann Lab Med 2022;42:630~637 https://doi.org/10.3343/alm.2022.42.6.630