THE ASSESSMENT OF THE QUASIMEME LABORATORY PERFORMANCE STUDIES DATA -TECHNIQUES AND APPROACH

A detailed assessment programme has been developed by the QUASIMEME Sc ientific Assessment Group to evaluate the results of the five rounds o f the interlaboratory studies for the main mandatory chemical determin ands in European Marine Monitoring Programmes. Two robust statistical algorithms were evaluated and one applied systematically to the study data. The established method of evaluation dealt with zero values, les s than' values, skewed distributions, bimodal distributions from metho dologically defined measurements and extreme values differing by facto rs of 2 to 1000 from the assigned value. Data from reference laborator ies and declared concentrations from the sample preparation were, in t he main, used to establish the assigned values. Z Scores were used to assess the laboratory performance. The sum of the number of satisfacto ry Z scores was used as an indicator of performance for successive int er-laboratory studies. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.