INTERACTIVE PROGRAM FOR EVALUATION OF CIRCULAR ANALYSES (IPECA)

A PC-based interactive programme is described which is designed to help in suggesting the best estimate of the true value of an analyte content from results of collective studies aiming at deriving consensus values and/or reference material preparation by employing combined statistical and analytical considerations. The Grubbs, Dixon, Huber tests, and the coefficients of skewness and curtosis tests are used for outlier detection, the Bartlett, Cochran, and the standard error tests are employed for testing variance homogeneity testing and/or variance outliers identification, while the normality of results distribution is rested according to the Kolmogoroff-Smirnoff-Lilliefors and Shapiro-Wilk tests. One-way analysis of variance (ANOVA) is employed to test differences among means of results obtained in different conditions (laboratories, analytical methods, etc.) and to calculate the overall mean and its confidence interval accordingly. Points for an analytical discussion are given which should be considered prior to a decision whether a result of a trace element determination, identified as an outlier from statistical reasons, should be rejected.