ISO 5667-20:2008建立了原则、基本要求和说明性方法，用于根据水质:满足目标和符合阈值的置信度评估，处理决策中使用样本数据的问题；改变了；和/或位于分类系统中的特定等级。 ISO 5667-20:2008还规定了初步检查决策对错误和不确定性敏感性的方法，尽管它没有涵盖所有统计技术。 ISO 5667-20:2008提供了与阈值和目标的表达以及抽样计划的形式和规模的约束制定相关的决策一般建议。

ISO 5667-20:2008 establishes principles, basic requirements, and illustrative methods for dealing with the use of sample data for decision making based on the assessment of the confidence that water quality: meets targets and complies with thresholds; has changed; and/or lies in a particular grade in a classification system. ISO 5667-20:2008 also specifies methods for preliminary examination of the sensitivity of decisions to error and uncertainty, although it does not cover the full range of statistical techniques. ISO 5667-20:2008 provides general advice on decision making related to constraint formulation for expression of thresholds and targets and the form and scale of sampling programmes.