Comparison of alternative measurement methods

A procedure to compare the performance (precision and bias) of an alternati ve measurement method and a reference method has been extensively described . It is based on ISO 5725-6 which has been adapted to the intralaboratory s ituation. This means that the proposed approach does not evaluate the repro ducibility, but considers the (operator+instrument+time)-different intermed iate precision and/or the time-different intermediate precision. A 4-factor nested design is used for the study. The calculation of different variance estimates from the experimental data is carried out by ANOVA. The Satterth waite approximation is included to determine the number of degrees of freed om associated with the compound variances. Taken into account the acceptabl e bias, the acceptable ratio between the precision parameters of the two me thods, the significance level or and the probability beta to wrongly accept an alternative method with an unacceptable performance, the formulae to de termine the number of measurements required for the comparison are given. F or the evaluation of the bias, in addition to the point hypothesis testing, the interval hypothesis testing is also included as an alternative. Two ex amples are given as an illustration of the proposed approach. (C) 1999 Else vier Science B.V. All rights reserved.