Overview
ISO/IEC Guide 98-5:2026 (Guide to the Expression of Uncertainty in Measurement - Part 5: Examples) is a vital resource for professionals involved in measurement science, quality assurance, metrology, and laboratory operations. Published by ISO and IEC, this guide forms part of the GUM (Guide to the Expression of Uncertainty in Measurement) series. It focuses on providing detailed, illustrative examples that demonstrate the practical application of uncertainty evaluation methods as described in the GUM suite. By offering real-world case studies, this document supports the correct implementation of measurement uncertainty best practices across diverse scientific and industrial domains.
Key Topics
- Worked Examples: The guide delivers comprehensive, step-by-step examples covering key concepts in measurement uncertainty. Topics range from pH measurement and analytical chemistry to gauge block calibration and conformity assessment.
- Uncertainty Propagation: Showcases propagation methods such as the law of propagation of uncertainty (LPU) and the Monte Carlo method (MCM), for both single-value (univariate) and multivariate quantities.
- Measurement Models: Explores calibration models including two-point and multi-point linear interpolation, highlighting how to construct and use measurement models for uncertainty assessment.
- Validation and Reporting: Illustrates best practices for reporting measurement results, including the determination of coverage intervals, risk analysis within conformity assessment, and ensuring results are communicated with traceable uncertainty statements.
- Comparative Methods: Presents comparisons between conventional approaches and alternative methods, such as least-squares versus Bayesian inference in calibration, highlighting strengths and considerations for practical use.
Applications
ISO/IEC Guide 98-5:2026 is designed for seamless integration across a variety of professional and technical disciplines. Its case studies and methods can be applied in:
- Calibration Laboratories: Ensuring robust evaluation and reporting of uncertainties in instrument calibration.
- Environmental Monitoring: Supporting the assessment and reporting of uncertainty in greenhouse gas emission inventories and particulate matter measurements.
- Healthcare and Life Sciences: Assisting in the evaluation of uncertainty for clinical measurements, such as mass estimations from medical imaging or reference material homogeneity.
- Industrial Quality Assurance: Applying measurement uncertainty in the conformity assessment of products such as steel wire ropes or complex analytical mixtures.
- Research and Academia: Providing reference material for teaching uncertainty evaluation methods or developing measurement models for scientific research.
- Accreditation and Certification: Supporting laboratories in fulfilling the requirements for ISO/IEC 17025 and similar accreditation schemes that rely on rigorous uncertainty assessment and documentation.
Related Standards
Professionals using ISO/IEC Guide 98-5:2026 may also benefit from referencing related standards and guidance documents within the GUM suite and international metrology frameworks, including:
- JCGM 100:2008 – Guide to the Expression of Uncertainty in Measurement (GUM)
- JCGM 101:2008 – Supplement 1: Propagation of Distributions Using a Monte Carlo Method
- JCGM 102:2011 – Supplement 2: Extensions to Any Number of Output Quantities
- JCGM 106:2012 – The Role of Measurement Uncertainty in Conformity Assessment
- ISO/TS 28037 – Determination and Use of Straight-Line Calibration Functions
- VIM (International Vocabulary of Metrology) – For general terminology and definitions
Practical Value
By adopting the approaches in ISO/IEC Guide 98-5:2026, organizations and professionals benefit from:
- Improved measurement quality and reliability through standardized uncertainty evaluation.
- Enhanced credibility and traceability of measurement results, supporting compliance with regulatory and accreditation requirements.
- Efficient training resource through worked examples aiding understanding and practical implementation of GUM principles.
- Facilitated risk-informed decision-making in conformity assessment and regulatory reporting.
For anyone seeking to implement internationally recognized measurement uncertainty practices, ISO/IEC Guide 98-5:2026 serves as an essential, example-driven complement to the foundational GUM documents.