ASTM E177:20 pdf download

ASTM E177:20 pdf download.Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods.
4. Significance and Use
4.1 Part A of the ‘Blue Book,” Form and Style for ASTM Standards, requires that all test methods include statements of precision and bias. This practice discusses these two concepts and provides guidance for their use in statements about test methods.
4.2 Precision—A statement of precision allows potential users of a test method to assess in general terms the test method’s usefulness with respect to variability in proposed applications. A statement of precision is not intended to exhibit values that can he exactly duplicated in every user’s laboratory. Instead, the statement provides guidelines as to the magnitude of variability that can be expected between test results when the method is used in one, or in two or more, reasonably competent laboratories. For a discussion of precision, see 8. I.
4.3 Bias-A statement of bias furnishes guidelines on the relationship between a set of typical test results produced by the test method under specific test conditions and a related set of accepted reference values (see 9.1).
4.3.1 An alternative term for bias is trueness, which has a positive connotation, in that greater bias is associated with less favorable trueness. Trueness is the systematic component of accuracy.
4.4 curacy—The term “accuracy,” used in earlier editions of Practice E177, embraces both precision and bias (sec 9.3).
5. Test Method
5.1 Section 2 of the ASTM Regulations describes a test method as “a definitive procedure for the identification, measurement, and evaluation of one or more qualities, characteristics, or properties of a material, product, system or service that produces a test result.”
5.2 In this practice only quantitative test methods that produce numerical results are considered. Also, the word “material” is used to mean material, product, system or service; the word “property” is used herein to mean that a quantitative test result can be obtained that describes a characteristic or a quality, or some other aspect of the material; and “test method” refers to both the document and the procedure described therein for obtaining a quantitative test result for one property. For a discussion of test result, see 7.1.
5.3 A well-written test method specifies control over such factors as the test equipment, the test environment, the qualifications of the Operator (explicitly or implicitly), the preparation of test specimens, and the operating procedure for using the equipment in the test environment to measure some property of the test specimens. The test method will also specify the number of test specimens required and how measurements on them are to be combined to provide a test result (7.1), and might also reference a sampling procedure appropriate for the intended use of the method.
5.4 It is necessary that the writers of the test method provide instructions or requirements for every known outside influence.