Overview - ISO/IEC Guide 98-1:2024 (GUM Part 1: Introduction)
ISO/IEC Guide 98-1:2024 is the second edition of Part 1 of the Guide to the Expression of Uncertainty in Measurement (the GUM). Prepared by the Joint Committee for Guides in Metrology (JCGM) and identical to JCGM GUM‑1:2023, this document provides an authoritative introduction and rationale for the evaluation, expression and use of measurement uncertainty. It is intended to be applicable across a wide spectrum of measurement activities - from the shop floor to fundamental research - and orients readers to the full GUM suite (see Annex A and Annex ZZ for lists and correspondences).
Key topics and technical requirements
- Scope and rationale: Explains why uncertainty statements are essential for decision making, conformity assessment and comparability of results (Clause 1–2).
- Fundamental concepts of measurement: Defines the measurand, measured value (estimate), true value, and the role of measurement standards and metrological traceability (Clause 3).
- Forms of expressing uncertainty: Introduces common expressions such as standard uncertainty, expanded uncertainty (with coverage factor), coverage intervals with coverage probability, and probability distributions for representing knowledge about a measurand (Clause 3.4).
- Guidance on evaluation: Emphasizes that evaluating measurement uncertainty is not purely mathematical but depends on detailed understanding of the measurement process and the measurand (Clause 4).
- Orientation to the GUM parts: Summarizes other GUM documents that provide detailed procedures - e.g. the law of propagation of uncertainty (JCGM 100), propagation of distributions (JCGM 101), extensions to multivariate outputs (JCGM 102), measurement models (JCGM GUM‑6) and conformity assessment (JCGM 106) (Clause 5 and Annex A).
Practical applications and users
ISO/IEC Guide 98-1:2024 is essential for anyone who needs to evaluate, report or interpret measurement uncertainty:
- Calibration and testing laboratories (supports ISO/IEC 17025 compliance)
- Reference material producers (ISO 17034), medical laboratories (ISO 15189), and proficiency testing providers (ISO/IEC 17043)
- Accreditation bodies, regulators and conformity assessment bodies
- Metrology institutes, R&D and QA/QC teams in industry and manufacturing
- Software developers implementing uncertainty propagation and reporting tools
Benefits include harmonized uncertainty reporting, improved comparability of results, better informed decision making, and support for mutual recognition of calibration certificates and accreditations.
Related standards and guidance
Use ISO/IEC Guide 98-1:2024 as the concise introduction to the GUM framework before applying the detailed procedures in the companion GUM parts for rigorous measurement uncertainty evaluation and reporting.