Fearn T, Thompson M
Department of Statistical Science, University College London, UK.
Analyst. 2001 Aug;126(8):1414-7. doi: 10.1039/b103812p.
Certified reference materials and materials distributed in proficiency testing need to be 'sufficiently homogeneous', that is, the variance in the mean composition of the distributed portions of the material must be negligibly small in relation to the variance of the analytical result produced when the material is in normal use. The requirement for sufficient homogeneity suggests the use of a formal test. Such tests as have been formulated rely on the duplicated analysis of the material from a number of portions, followed by analysis of variance. However, the outcome is not straightforward. If the analytical method used is very precise, then an undue proportion of the materials will be found to be significantly heterogeneous. If it is too imprecise, the test may be unable to detect heterogeneity. Moreover, the Harmonised Protocol Procedure (M. Thompson and R. Wood, Pure Appl. Chem., 1993, 65, 2123) seems to be unduly prone to the rejection of material that is in fact satisfactory. We present a simple new statistical approach that overcomes some of these problems.
认证参考物质和能力验证中分发的物质需要“足够均匀”，也就是说，相对于该物质在正常使用时产生的分析结果的方差而言，所分发部分物质的平均组成中的方差必须小到可以忽略不计。对足够均匀性的要求意味着要使用一种正式的测试。已制定的此类测试依赖于对多个部分的物质进行重复分析，然后进行方差分析。然而，结果并非一目了然。如果所使用的分析方法非常精确，那么就会发现有过多比例的物质存在显著的不均匀性。如果该方法不够精确，测试可能无法检测到不均匀性。此外，协调协议程序（M. 汤普森和R. 伍德，《纯粹与应用化学》，1993年，65卷，2123页）似乎过于容易拒绝实际上令人满意的物质。我们提出了一种简单的新统计方法，该方法克服了其中的一些问题。
