Evaluation of geochemical sedimentary reference materials of the Geological Survey of Japan (GSJ) by an objective outlier rejection statistical method

Abstract

Nine geochemical sedimentary reference materials (RMs), JCh-1, JDo-1, JLs-1, JSl-1, JSl-2, JLk-1, JSd-1, JSd-2 and JSd-3, of the Geological Survey of Japan (GSJ) were evaluated by an objective outlier rejection statistical method. An extensive chemical database for these reference materials, created from the Internet website of the GSJ Geochemical Reference Samples Database (http://riodb02.ibase.aist.go.jp/geostand/) and from research articles published up to December 2008, is evaluated by a statistical scheme consisting of: (i) detection and elimination of the discordant outlier values with the application of 33 discordancy test variants (instead of routinely used inaccurate “two-standard deviation” method); (ii) calculation of new central tendency and dispersion parameters; and (iii) comparison of confi dence limits (calculated by incorporating the recently available new, precise critical values for Student t-test) and normalized mean difference percentages of the geochemical parameters obtained in the present work with those calculated for the data of the literature. Evaluation of these RMs by application of the more appropriate statistical method resulted in more precise new central tendency and dispersion parameter values, and also facilitated to propose recommended values for the fi rst time for some of the geochemical parameters. The results obtained in this work could be useful for better calibrations models and for evaluation of method precision, accuracy, sensitivity and detection limits.