BS ISO 5725-1:1994

Committees responsible
National foreword
Foreword
Introduction
1 Scope
2 Normative references
3 Definitions
4 Practical implications of the definitions for
    accuracy experiments
    4.1 Standard measurement method
    4.2 Accuracy experiment
    4.3 Identical test items
    4.4 Short intervals of time
    4.5 Participating laboratories
    4.6 Observation conditions
5 Statistical model
    5.1 Basic model
    5.2 Relationship between the basic model and the
          precision
    5.3 Alternative models
6 Experimental design considerations when estimating
    accuracy
    6.1 Planning of an accuracy experiment
    6.2 Standard measurement method
    6.3 Selection of laboratories for the accuracy
          experiment
    6.4 Selection of materials to be used for an
          accuracy experiment
7 Utilization of accuracy data
    7.1 Publication of trueness and precision values
    7.2 Practical applications of trueness and
          precision values
Annex A (normative) Symbols and abbreviations used in
         ISO 5725
Annex B (normative) Charts of uncertainties for
         precision measures
Annex C (informative) Bibliography
Figure B.1 - The amount by which sr can be expected to
             differ from the true value within a
             probability level of 95 %
Figure B.2 - The amount by which sR can be expected to
             differ from the true value within a
             probability level of 95 %
Table 1 - Values showing the uncertainty of estimates
          of the repeatability and reproducibility
          standard deviations
Table 2 - Values of A, the uncertainty of an estimate
          of the bias of the measurement method
Table 3 - Values of AW, the uncertainty of the
          within-laboratory bias
Table 4 - Example of method of reporting standard
          deviations

Outlines the general principles to be understood when assessing accuracy of measurement methods and results. Concerned exclusively with measurement methods which yield measurements on a continuous scale and give a single value as the test result. Defines values which describe, in quantitative terms, the ability of a measurement method to give a correct result (trueness) or to replicate a given result (precision). Coverage includes: practical implications of the definitions for accuracy experiments; experimental design considerations when estimating accuracy; relationship between the basic model and the precision. Also gives definitions.

1.1 The purpose of ISO5725 is as follows: to outline the general principles to be understood when assessing accuracy (trueness and precision) of measurement methods and results, and in applications, and to establish practical estimations of the various measures by experiment (ISO5725-1); to provide a basic method for estimating the two extreme measures of the precision of measurement methods by experiment (ISO5725-2); to provide a procedure for obtaining intermediate measures of precision, giving the circumstances in which they apply and methods for estimating them (ISO5725-3); to provide basic methods for the determination of the trueness of a measurement method (ISO5725-4); to provide some alternatives to the basic methods, given in ISO5725-2 and ISO5725-4, for determining the precision and trueness of measurement methods for use under certain circumstances (ISO5725-5); to present some practical applications of these measures of trueness and precision (ISO5725-6). 1.2 This part of ISO5725 is concerned exclusively with measurement methods which yield measurements on a continuous scale and give a single value as the test result, although this single value may be the outcome of a calculation from a set of observations. It defines values which describe, in quantitative terms, the ability of a measurement method to give a correct result (trueness) or to replicate a given result (precision). Thus there is an implication that exactly the same thing is being measured, in exactly the same way, and that the measurement process is under control. This part of ISO5725 may be applied to a very wide range of materials, including liquids, powders and solid objects, manufactured or naturally occurring, provided that due consideration is given to any heterogeneity of the material.