ISO 5725-2:2019

Overview

ISO 5725-2:2019 (equivalent to ISO 5725-2:2019) defines the basic method for estimating the precision of a standard measurement method by means of a collaborative interlaboratory experiment. It amplifies the principles in ISO 5725‑1 and gives practical, routine procedures for determining the two principal precision characteristics: repeatability and reproducibility. The standard applies to measurement methods that produce a single continuous numeric result (including results derived from calculations of observations) and assumes data are approximately normally distributed.

Key technical topics and requirements

• Experimental design: Uses a balanced, uniform‑level layout where each laboratory performs the same number of replicates on the same sample levels.
• Scope of applicability: Intended for standardized procedures in regular use; can also provide preliminary precision estimates for non‑standard methods.
• Material considerations: Requires homogeneous test materials or that heterogeneity effects be included in precision estimates.
• Statistical model: Builds on the ISO 5725‑1 statistical model for interpretation and variance component estimation.
• Personnel and roles: Defines responsibilities for panels, statistical experts, supervisors and operators involved in precision experiments.
• Data scrutiny and outlier handling: Describes graphical and numerical techniques for consistency checks and outlier detection (e.g., Cochran’s and Grubbs’ tests) and permits alternative methods of similar performance.
• Variance estimation & analysis: Details calculation of cell means, measures of spread, general mean and variance components, and fitting functional relationships between precision and mean level.
• Reporting: Specifies reporting requirements to the study panel and content of the full report.
• Supporting material: Annexes include guidance on the number of laboratories needed, alternative variance calculations and worked examples.

Practical applications and users

SIST ISO 5725-2 is essential for:

• Metrology and testing laboratories validating or verifying method precision
• Method developers preparing standardized analytical procedures
• Accreditation bodies and quality managers assessing laboratory competence
• Proficiency testing organizers designing interlaboratory studies
• Statisticians performing precision analyses and uncertainty estimation workflows

Typical uses include method validation, interlaboratory comparison studies, development of performance characteristics for standards, and inputs to measurement uncertainty and conformity assessment.

Related standards

• ISO 5725‑1 - general principles and definitions for accuracy (trueness and precision)
• Other parts of ISO 5725 series - modifications and extensions for particular experimental designs
• ISO 21748 - using interlaboratory estimates of precision and trueness for measurement uncertainty

Keywords: ISO 5725-2, ISO 5725-2:2019, accuracy, trueness, precision, repeatability, reproducibility, interlaboratory experiment, balanced uniform-level, statistical analysis.