ASTM D7778-15(2022)e1

SIGNIFICANCE AND USE 5.1 All ASTM standard test methods are required to include statements on precision and bias. To obtain such data it is necessary to conduct an interlaboratory study. This document is designed to provide a brief overview of the steps necessary in an ILS and to suggest an appropriate sequence in carrying out these steps. 5.1.1 Qualitative tests such as Test Method D130 copper corrosion may not require an ILS. SCOPE 1.1 This guide describes the procedures for planning and conducting an interlaboratory study (ILS) of a test method used in Petroleum Products and Lubricants Committee D02 of ASTM for the purpose of estimating repeatability and reproducibility of the test method in accordance with ASTM Form and Style requirements. 1.2 This guide is concerned with the management of the ILS and intended to provide guidance for the planning stage and ensure the process, logistics, and tools are identified and agreed upon in advance. 1.2.1 Selection of the samples and the impact of sample selection on the final scope of the test method—both the range of materials covered in the scope and precision sections and the measurement range covered in the precision section—are important, and careful consideration needs to be given to these aspects before an ILS is launched. 1.3 This guide does not concern itself with the development of test methods but rather with gathering the information needed for a test method precision statement. 1.4 This guide is concerned with test methods which yield a single numerical figure as the test result, although the single figure may be the result of a calculation from a set of measurements. 1.5 This guide is designed for tests of properties that are stable, such that bulk samples can be homogenized and sub-samples can be prepared that will be identical and stable for the duration of the ILS testing period. This guide is not designed for unstable properties or for properties that make it difficult to obtain stable, representative samples for an ILS conducted at multiple laboratory sites. 1.6 This guide represents the suggested practices for a typical precision study. Individual subcommittees may modify this approach as their expertise directs. 1.7 This guide is voluntary, and thus, is not required for an approved precision study. 1.8 This 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.