EQAS Program User Guide - QCNet

CHAPTER7Statistics and Algorithms Used inEQAS ReportsIn This ChapterStatistics Used in the Sample Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Statistics Used in the End-of-Cycle Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88Method Summary and Subgroup Report Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Statistics Used in the Sample ReportNThe number of results received. Defines the number of data points in the data set.Robust MeanThe estimate of the population mean using a robust algorithm. Refer to the International Standard, ISO 13528(2005), Annex C, Robust analysis, Algorithm A for more information.Robust Standard Deviation ()The estimate of the population standard deviation using a robust algorithm. Refer to the InternationalStandard, ISO 13528 (2005), Annex C, Robust analysis, Algorithm A for more informationNon-robust Mean (x) and Standard Deviation (SD)The traditional mean and SD calculation formulas. In some circumstances, the robust statistical process maynot be used to evaluate the comparator statistics. In such cases “traditional” statistics are used. The use oftraditional (non-robust) statistics occurs in cases where the consensus group’s standard deviation is zero. Thisis encountered when 50% or more of the results submitted are of the same value.Calculate the non-robust mean (x)x =x n /nWhere: = sumx n = each value in the data setn = the number of values in the data setBio-Rad Laboratories 85