PARTICIPANT’S GUIDE EXTERNAL QUALITY ASSESSMENT SCHEMES

The variability (%) indicated in the report is then calculated by replacing the standard deviation and the arithmetic mean with the robust standard deviation and the robust average of the Algorithm A. [...] Similarly, if the method of calculation of the AV is in fact the median, the standard deviation and the arithmetic mean are replaced by the standard deviation from MAD and the median to obtain the calculation of the variability (%). [...] Since the default method used to calculate the AV is the robust mean according to the Algorithm A (1.3.2), the standard uncertainty of the AV will be default calculated according to the formula described in Section 1.3.8.1. [...] When the normality hypothesis is rejected, the use of robust methods for the determination of the AV by consensus such as the Algorithm A allows to obtain a better estimation of the AV. [...] The result of the normality of the distribution of each set of observations is provided in the report whether the test is “Accepted” or “Rejected” under the column labeled “KS (Lilliefors)” Proficiency Standard Deviation (σpt) The standard deviation for proficiency testing is a measure of dispersion used in the evaluation of proficiency.