The second edition of ISO 19229 expands the guidance in its predecessor in two ways. Firstly, it provides more support and examples describing possible experimental approaches for purity analysis. A novelty is that it describes how the beta distribution or some other suitable probability distribution can be used to approximate the distribution of the output quantity, i.e. the fraction of a component. It also provides guidance on how to report coverage intervals in those cases, where the usual approximation from the Guide to the Expression of Uncertainty in Measurement to use the normal or t distribution is inappropriate because of vicinity of zero. Coverage intervals play an important role in conformity assessment, and it is also customary to report measurement uncertainty in the form of a coverage interval, notwithstanding that ISO/IEC 17025 does not explicitly require it. ISO 6141, which sets requirements for certificates of calibration gas mixtures, does require the statement of an expanded uncertainty, which has been interpreted that in the case of a non-symmetric output probability distribution, a coverage interval should be stated, along with the value and the standard uncertainty. This paper gives a brief background to the choices made and examples in ISO 19229.

中文翻译：

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修订 ISO 19229 以支持校准气体的纯度认证

ISO 19229 第二版以两种方式扩展了其前身的指南。首先，它提供了更多的支持和示例，描述了纯度分析的可能实验方法。新颖之处在于它描述了如何使用 beta 分布或一些其他合适的概率分布来近似输出量的分布，即组件的分数。它还提供了在这些情况下如何报告覆盖区间的指导，在这些情况下，由于接近零，测量不确定性表达指南中使用正态分布或 t 分布的通常近似值是不合适的。覆盖区间在合格评定中起着重要作用，通常也以覆盖区间的形式报告测量不确定性，尽管 ISO/IEC 17025 没有明确要求。ISO 6141 对校准气体混合物的证书设定了要求，确实要求声明扩展不确定度，这被解释为在非对称输出概率分布的情况下，应说明覆盖区间以及值和标准不确定度。本文简要介绍了 ISO 19229 中的选择和示例。