TS ISO 5725-1

TS ISO 5725-1 sets out the core concepts and common framework for the ISO 5725 series, which addresses accuracy in measurement methods and results through trueness and precision. This part establishes the general principles, organisational approach and statistical basis used to assess how well a measurement method produces results, so that the terminology and evaluation logic used in the later parts of the series rest on the same foundation.

What trueness and precision mean in practice

In general technical terms, trueness describes how close a measurement result is to the true value, while precision describes how closely repeated results agree with one another. The two are related but not identical: a method may give highly consistent results and still be offset from the true value by systematic error. This part of the standard defines the conceptual framework for describing those two properties quantitatively.

Where the standard applies, and where it does not

The scope is limited to measurement methods that produce a single result on a continuous scale, even when that result is calculated from several observations. It is intended for a wide range of test items, including gases, liquids, powders and solid objects, but the heterogeneity of the material must be taken into account. Proficiency testing and the production of reference items are outside this part because they are covered by separate standards.

• Defines the conditions, constraints and resources needed to evaluate a measurement method or result.
• Sets out an organisational scheme for acquiring trueness and precision data through a study.
• Provides the definitions, statistical model and principles used across ISO 5725.
• Focuses on methods that yield one result on a continuous scale.
• Separates its subject from proficiency testing and reference item production.