scope:

The analysis methods outlined in this document provide a comprehensive approach to estimating measurement uncertainty. Basic guidelines are presented for estimating the uncertainty in the value of a quantity for the following measurement alternatives:

• Direct Measurements - The value of a quantity is obtained directly by measurement and not determined indirectly by computing its value from the values of other variables or quantities.

• Multivariate Measurements - The value of the quantity is based on measurements of more than one attribute or quantity.

• Measurement Systems - The value of a quantity is measured with a system comprised of component modules arranged in series.

The structured, step-by-step uncertainty analysis procedures described herein address the important aspects of identifying measurement process errors and using appropriate error models and error distributions. Advanced topics cover estimating degrees of freedom for Type B uncertainties, uncertainty analysis for alternative calibration scenarios, uncertainty growth over time and Bayesian analysis.

Examples contained in the main body of this document provide detailed step-by-step analysis procedures that re-enforce important principles and methods. Analysis examples included in the appendices address real-world measurement scenarios and follow a standardized format to clearly convey the necessary information and concepts used in each analysis.

Purpose

While the GUM provides general rules for analyzing and communicating measurement uncertainty, it does not provide detailed procedures or instructions for evaluating specific measurement processes.2 In addition, new methods have been developed over the past several years that enhance the methodology of the GUM.

This document provides a recommended practice that clearly explains key concepts and principles for estimating and reporting measurement uncertainty. This document also includes advanced methods that extend the GUM's guidance on estimating measurement uncertainty.