1.1This guide presents techniques and guidance for evaluating and assuring homogeneity of individual samples and bulk materials used for interlaboratory and intra-laboratory studies.

1.2This guide is applicable to samples and reference materials used for proficiency testing programs and for interlaboratory studies to determine precision estimates for test methods. It may also be useful for activities related to quality control of testing within a single laboratory.

1.3Five techniques are presented for assessing sample homogeneity. The five techniques are not an exhaustive list of available techniques for assessing homogeneity of samples, but the techniques were chosen to cover a range of circumstances (and various degrees of rigor required) for laboratory studies of various types and purposes.

1.4Each of the first four techniques provides a scheme for testing for homogeneity and a statistical procedure for evaluating the results of the homogeneity testing. The circumstances are described for which each of the techniques is suited.

1.5For circumstances when homogeneity testing is not possible, the fifth technique provides guidance for producing homogeneous samples.

1.6The appendixes of this guide provide example spreadsheets for Techniques 1, 2, 3, and 4.

1.7This guide is not intended for evaluation of certified reference materials (CRMs) or materials used for calibration.

1.8Units—The system of units for this standard is not specified. Dimensional quantities in the standard are presented only as illustrations of calculation methods. The examples are not binding on products or test methods treated.

1.9This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.10This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.