Empirical relationship providing a standard deviation under reproducibility conditions of measurement (
\(s_{\rm{R,H}}\)) to be expected for typical measurements of the mass fraction (
\(w\)) of a component in a material:
\(s_{\rm{R,H}} = 0.02 w^{0.8495}\).
Note: The shape of the curve is called a trumpet when the relative standard deviation is plotted against the logarithm of the mass fraction as shown in Fig. 1. The reference justifies the mirror curve for negative ordinate values by "… the lines are best regarded as confidence boundaries."
Source:
PAC, 2021, 93, 997. 'Metrological and quality concepts in analytical chemistry (IUPAC Recommendations 2021)' on page 1026 (https://doi.org/10.1515/pac-2019-0819)