Algorithm 1. Algorithm used to calculate the robust average Eref and robust standard deviation s* taken from ISO 13528:2015 denoted as Algorithm A. The parameters are updated following the steps 3 and 4 iteratively until the process converges.

1: There are p items of results denoted as:

$E_i=E_1,E_2,E_3,\dots ,E_p$

2: Calculate initial values for $E_{ref}$ $\mathrm{and}{s}^{*}$ as:

$E_{ref}=\mathrm{median}\mathrm{of} E_i$

$s^{*}=1.483\mathrm{median}\mathrm{of} |E_i-E_{ref}|$

3: Update the values of $E_{ref}$ $\mathrm{and}{s}^{*}$ as follows. Calculate:

$\delta =1.5s^{*}$

$E_i^{*}=\{\begin{array}{ccc}{E}_{ref}-\delta & \mathrm{when}& E_i<E_{ref}-\delta \\ E_{ref}+\delta & \mathrm{when}& E_i>E_{ref}+\delta \\ E_i& \mathrm{otherwise}& \end{array}$

4: Calculate the new values of $E_{ref}$ and $s^{*}$ from:

$E_{ref}=\mathrm{mean}\mathrm{of}{E}_i^{*}$

$s^{*}=1.134·\mathrm{SD}(E_i^{*}$)