ISO/TR 9272:2005

ISO/TR 9272:2005 presents guidelines for determining, by means of interlaboratory test programmes (ITPs), precision for test method standards used in the rubber manufacturing and the carbon black industries. It uses the basic one-way analysis of variance calculation algorithms of ISO 5725 and as many of the terms and definitions of ISO 5725 as possible that do not conflict with the past history and procedures for precision determination in these two industries. Although bias is not determined in this Technical Report, it is an essential concept in understanding precision determination. The ISO 5725 concepts of accuracy and trueness are not determined in this Technical Report. Two precision determination methods are given that are described as 'robust' statistical procedures that attempt to eliminate or substantially decrease the influence of outliers. The first is a 'level 1 precision' procedure intended for all test methods in the rubber manufacturing industry and the second is a specific variation of the general precision procedure, designated 'level 2 precision', that applies to carbon black testing. Both of these use the same uniform level experimental design and the Mandel h and k statistics to review the precision database for potential outliers. However, they use slight modifications in the procedure for rejecting incompatible data values as outliers. The 'level 2 precision' procedure is specific as to the number of replicates per database cell or material-laboratory combination.