EQAS Program User Guide - QCNet

Chapter 9: GlossaryRMZRunning Mean Z-score. An ongoing (within or across cycles) average of the Z-scores of the last six samplesfor a given analyte.Robust MeanAn estimate of the dataset mean using a robust algorithm. This algorithm calculates the mean and standarddeviation of the dataset through an iterative statistical process. For additional information, refer to theInternational Standard, ISO 13528 (2005), Annex C, Robust analysis, Algorithm A.Robust StatisticsRobust statistics are based on the assumption that a given dataset exhibits a normal distribution of measuredvalues contaminated with a small portion of outliers. The robust statistic is not excessively affected by theoutliers. These statistics are calculated by downweighting the data points that are distant from the mean andthen compensating for that downweighting.Sample CloseA sample is closed on the Sample Due Date. This is when the dataset is established and a statistical analysisis performed to provide each reporting laboratory a comparison of their performance for that sample.Sample Due DateThe date on which a sample’s results are to arrive at Bio-Rad EQAS for the statistical analysis. The results willbe accepted until 20:00 GMT time on the specified date. Sample Due Dates are displayed for each EQASProgram on the sample vial label and in various documents, including the Results Forms. Results receivedafter this due date will be represented as late in the EQAS reports.Standard Deviation (SD)A statistic that quantifies the degree of dispersion or spread of a set of data points around the mean value of aGaussian or normal distribution.Standard Deviation Index (SDI)A statistical measure that is expressed as Z-score in the EQAS Program.SubgroupA group or collective of laboratories with a common interest in an EQAS Program. These laboratories aregrouped together in special reports that are generated and distributed to a designated subgroup leader.102 EQAS Program User Guide