In eCerto: Statistical Tests for the Production of Reference Materials

Calculation of possible storage time

When a certified value $\mu_c$ and corresponding uncertainty $U_{abs}$ (cert_val and U_abs) are available for an analyte in Tab.C3 of the certification module of eCerto, these can be used together with $\mathit{CI}{upper}$ from Tab.S2 to calculate the storage time $S{Month}$ for each evaluated temperature level using:

$$S_{\mathit{Month}}(T) = \frac{ \log( \frac{\mu_c - U_{abs}}{\mu_c})}{e^{\mathit{CI}_{upper}(T)} }$$

Note! It is recommended to use $\mu_c$ and $U_{abs}$ for these calculations. However, the user can alternatively use mean and 2 x standard deviation from the stability data of the reference temperature as an approximation by selecting the respective radio-button. Also, a direct input of the coefficient used in the above equation $\log(\frac{\mu_c - U_{abs}}{\mu_c})$ is possible.