ISO/TS 21749:2005遵循测量不确定度表达指南(GUM)中采用的方法，并建立了陈述和组合不确定度分量的基本结构。在这一基本结构中，它增加了一个使用方差分析（ANOVA）的统计框架，用于估计单个组件，特别是那些被归类为A类不确定性评估的组件，即基于使用统计方法。为完整起见，包括B类不确定性评估（非统计）的简短描述。 ISO/TS 21749:2005涵盖了可以通过重复测量、仪器、测试项目或检查标准的统计分析来估计不确定度分量的实验情况。 它提供了从单个-、两层和三层嵌套设计。不包括更复杂的实验情况，例如操作者效应和仪器效应之间存在相互作用或交叉效应。 ISO/TS 21749:2005不适用于无法复制的测量，如破坏性测量或动态变化系统（如流体流动、电子电流或电信系统）上的测量。它并不特别针对参考材料（特别是化学物质）的认证和使用称为“称重设计”的方案比较人工制品的校准。有关标准物质的认证，请参见ISO指南35。 当可以使用实验室间研究的结果时，相关技术见配套指南ISO/TS 21748。ISO/TS 21748与本技术规范之间的主要区别在于，ISO/TS 21748涉及再现性数据（具有不可避免的重复性影响），而本技术规范集中于再现性数据及其处理方差分析的使用。 ISO/TS 21749:2005适用于各种测量，例如长度、角度、电压、电阻、质量和密度。

ISO/TS 21749:2005 follows the approach taken in the Guide to the expression of the uncertainty of measurement (GUM) and establishes the basic structure for stating and combining components of uncertainty. To this basic structure, it adds a statistical framework using the analysis of variance (ANOVA) for estimating individual components, particularly those classified as Type A evaluations of uncertainty, i.e. based on the use of statistical methods. A short description of Type B evaluations of uncertainty (non-statistical) is included for completeness. ISO/TS 21749:2005 covers experimental situations where the components of uncertainty can be estimated from statistical analysis of repeated measurements, instruments, test items or check standards. It provides methods for obtaining uncertainties from single-, two- and three-level nested designs only. More complicated experimental situations where, for example, there is interaction between operator effects and instrument effects or a cross effect, are not covered. ISO/TS 21749:2005 is not applicable to measurements that cannot be replicated, such as destructive measurements or measurements on dynamically varying systems (such as fluid flow, electronic currents or telecommunications systems). It is not particularly directed to the certification of reference materials (particularly chemical substances) and to calibrations where artefacts are compared using a scheme known as a "weighing design". For certification of reference materials, see ISO Guide 35. When results from interlaboratory studies can be used, techniques are presented in the companion guide ISO/TS 21748. The main difference between ISO/TS 21748 and this Technical Specification is that the ISO/TS 21748 is concerned with reproducibility data (with the inevitable repeatability effects), whereas this Technical Specification concentrates on repeatability data and the use of the analysis of variance for its treatment. ISO/TS 21749:2005 is applicable to a wide variety of measurements, for example, lengths, angles, voltages, resistances, masses and densities.