ISO 5725-4:2020 pdf download – Accuracy (trueness and precision) of measurement methods and results — Part 4: Basic methods for the determination of the trueness of a standard measurement method.
Ideally, the choice of the combination of the number of laboratories and the number of replicate measurement results per laboratory should satisfy the requirement described by Formula (3), with the δ m value predetermined by the experimenter. However, for practical reasons, the choice of the number of laboratories is usually a compromise between the availability of resources and the desire to reduce the value of δ m to a satisfactory extent. If the reproducibility of the measurement method is poor, then it is not practical to achieve a high degree of certainty in the estimate of the bias. When σ R is larger than σ r (i.e. γ is larger than 1) as is often the case, little is to be gained by obtaining more than n = 2 measurement results per laboratory per level.
5.4 Requirements of the accepted reference value 5.4.1 Approaches to assigning the accepted reference value The accepted reference value of the property of interest, μ, shall be reliable and metrologically traceable to an accepted reference by which the true value can be substituted. It refers to the value carried by the material used in this experiment, which was either assigned in another independent study, such as the characterization of the reference material, the calibration of the measurement standard by using suitable calibration procedures and competent laboratories, the assignment by other measurement method (preferably a reference measurement method), or calculated from the property values of the materials used for preparation of the known sample. NOTE Guidance for the characterization and use of reference materials is given in ISO Guide 35 and ISO Guide 33, respectively. Refer to the definition for other measurement standards in ISO/IEC Guide 99 (VIM). 5.4.2 Materials used in the experiment 5.4.2.1 The material used in the experiment, whether purchased or prepared, can be a reference material, a measurement standard or a prepared known sample; it shall have the same property as that the standard measurement method is intended to be applied to, e.g. concentration.