5.1 This guide is intended for use by developers of RMs and CRMs for the metals and mining industries.

5.2 The guidance is related to uniform procedures and requirements and is intended to prevent the proliferation of widely varying documentation practices, definitions, and terminology. Where the statements in this guide are made as imperatives, it is because the stated practices are fundamental to chemical metrology, not to CRM/RM development.

5.3 The material in this guide is intended to supplement and to clarify the contents of ISO Guide 31 and to provide guidance specific to the needs of the metals and mining industries.

5.4 The documents described in this guide are intended to contain the minimum amount of information required for a user to understand the material, to help a user judge the quality of the product, and to help a user employ it in appropriate ways. Neither this guide nor resultant documents are meant to be encyclopedic.

5.5 Because this document is a standard guide, it is intended to educate those who are involved in laboratory operation, quality system development and maintenance, reference material development, and accreditation of laboratory operations within the scope of a quality system. It must be understood by all parties that the elements of this guide discuss optional practices having numerous choices for accomplishment and documentation. However, this guide does not constitute requirements for assessment and accreditation. An obvious example is statistical evaluation for consensus value and uncertainty calculations, which can take many forms with no single, correct choice for any given case.

5.6 When using this guide, CRM developers will set goals for the material under development, such as target uncertainties for homogeneity and for overall coverage intervals for assigned values. These choices are based on the intended uses of a CRM. The material, property values, and their uncertainties may or may not meet the set goals. These decisions are made using expert judgement, and there are no exact right or wrong, passing or failing outcomes that should be imposed by outside authorities. The quality of a CRM or RM will be judged by the prospective user, who needs it to use with their measurement process.

5.6.1 An example of a requirement a CRM user may have is whether the uncertainty of a certified value is fit for the purpose of using the value as a calibration point. CRM users and producers can obtain information from standard test methods or from laboratories doing relevant analyses.

5.6.2 Although the ISO Committee on Reference Materials (ISO TC334) has designated all CRMs and other forms of RMs as being named reference materials, this guide uses the convention the certified reference materials are called CRMs and reference materials having no certified values are named RMs. This practice is consistent with Guide E2972.