Significance and Use
4.1 This guide provides the developers of test methods with systematic approaches to evaluate the inherent adequacy (capability) of the precision and the adequacy of between-laboratory standardization as determined by interlaboratory testing in accordance with Practice for a new or modified test method.
4.1.1 The tools presented in this guide can be used to assess the adequacy of the repeatability and reproducibility determined for a given test method relative to their intended applications. For those test methods with less than optimal precision, the responsible subcommittees would have an opportunity to investigate, suggest improvements in the procedure, and design an interlaboratory study as necessary. It is important to note that non-optimal precision does not necessarily imply that the test method is invalid, but that the test method may be less capable for an intended application.
4.2 This guide is applicable to test method users to evaluate the relative performance of different test methods that purport to measure the same property as applied to a specific application of the test methods.
4.3 This guide can be used to evaluate the fitness for use of a test method reproducibility relative to its intended use in specifications.
4.3.1 When test method results are intended to be compared against specification limits, this guide provides the tools to assess whether the test method’s reproducibility is expected to be fit for use relative to the stated limits.
4.4 This guide is most effective when used in conjunction with sufficient knowledge of the chemistry, instrumental technology, metrology principles, sample characteristics, and a fundamental understanding of statistical meaning and implications associated with repeatability and reproducibility of the test method being evaluated.
4.5 This guide does not cover the qualitative and business factors that might also be considered in judging a test method’s capability or fitness for use versus a specific application.
1.1 This guide covers techniques for evaluating the statistical capability and fitness for use of standard test methods used for measuring properties of petroleum products, liquid fuels, and lubricants. Specifically, this guide provides strategies for evaluating the capability of a test method to provide a sufficiently precise estimate of the intended parameter versus a given level or value of that parameter and for assessing, with sufficient confidence, the fitness for use of a test method for determining the acceptability of products versus specification, regulatory, or manufacturing limits.
1.2 The assessment of capability in this guide is applicable to test methods that always yield non-negative numerical results and have a hard, fixed zero lower limit or fixed upper limit (for example, 100 %). Detailed knowledge of a test method and professional judgement may be required in determining the applicability of this guide to certain test methods.
1.3 In accordance with this guide, the assessment of fitness for use of a test method versus specification, regulatory, or manufacturing limits is generally applicable to test methods that provide numerical results and have applicable reproducibility precision values.
1.4 This guide is intended for use by test method developers, specification setters, and laboratories selecting test methods to evaluate products for specific purposes or versus specific limits.
1.5 This guide is not applicable to test methods that measure temperature to determine properties such as, but not limited to, freeze point, pour point, flash point, and distillations. This guide is not intended for use by laboratories for evaluating laboratory test method execution capability, nor is it intended to evaluate manufacturing process capability.
1.6 The expressions of capability and fitness for use derived from use of this guide should not be the only criteria for selection and use of a given test method. Other factors such as the laboratory’s experience with the test method, length of time to complete an analysis, typical product results relative to the regulatory or manufacturing specification limit, closeness of the results to zero, and cost factors may contribute more significantly to the decision to use a given test method for a specific application.
1.7 This guide draws on statistical approaches covered in other standards supporting petroleum products, liquid fuels, and lubricants, including Practices , , , , and ISO 4259.
1.8 This 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.
1.9 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.