EQAS Program User Guide - QCNet

Chapter 7: Statistics and Algorithms Used in EQAS ReportsMean Z-score ReportYour laboratory’s mean bias (mean absolute Z-score across all batches) is shown numerically for eachreported analyte. Also shown is a linear scale of the overall bias for the analyte for all participants in the samepeer group. The best 10%, 50%, and 90% is reflected on this scale with the participating laboratory’s meanmethod Z-score across all batches as a diamond shape.• A percentile value is calculated for each reported analyte. It indicates how your laboratory’s valuecorresponds to the location of the mean Z-score for the particular instrument and analyte combinationcompared to your peer group.• A lower percentile indicates better performance in relation to your comparator group.• If you are the only lab in the peer group, no comparison will be possible and a dash (-) will be displayed.National and Worldwide Performance Score Histograms• Your laboratory is ranked in quintiles based on your performance against national and overall participantsas two separate histograms.• The Y-axis is the number of laboratories.• The X-axis is unnamed and shows the “best” performance at the far left.• The laboratory’s overall performance is noted as to which quintile they fall in and scored based on thefollowing algorithms:– Late result: |Z-score| + 0.2– Amended result: |Z-score| + 0.4– Your laboratory’s results are then normalized based on the number of results reported.Method Summary and Subgroup Report StatisticsAll statistics presented in the Method Summary and Subgroup reports have been covered in the “StatisticsUsed in the Sample Report” section. Please refer to that section if additional information is required.EQAS Program User Guide 89