**Fig. 4. **
Difference in MU values between two differently calculated groups. (A) As the mean differences (%) increased, u_{rel_tot} values calculated regardless of mean change showed a constant MU, whereas usel_sub values calculated separately by mean and then combined showed gradual increases in MU. (B) MU differences (=%u_{rel_tot} – %u_{rel_sub}) with respect to mean differences (%) are plotted. For example, a mean difference of 10% after one reagent lot change corresponded to a difference in MU of 3.41%.

Abbreviations: MU, measurement uncertainty; u_{rel_tot}, relative uncertainty calculated regardless of a reagent lot change; u_{rel_sub}, relative combined uncertainty calculated from values obtained from each subgroup; %u_{rel}, relative uncertainty, akin to CV.

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