ASTM D4356-84(2002)

In any test method, every direction to measure a property of a material should be accompanied by a measurement tolerance. Likewise, determination and test result tolerances should be specified. This practice provides a method for evaluating the consistency of the test method tolerances specified.

This practice should be used both in the development of new test methods and in evaluating old test methods which are being revised.

The test result tolerance obtained using this practice is not a substitute for a precision statement based on interlaboratory testing. However, the measurement tolerances selected by means of this practice will be an important part of the test method conditions affecting the precision of the test method.

MATHEMATICAL RELATIONSHIPS

1.1 This practice should be used in the development of any test method in which the determination value is calculated from measurement values by means of an equation. The practice is not applicable to such determination values as those calculated from counts of nonconformities, ratios of successes to failures, gradings, or ratings.

1.2 The purpose of this practice is to provide guidance in the specifying of realistic and consistent tolerances for making measurements and for reporting the results of testing.

1.3 This practice can be used as a guide for obtaining the minimum test result tolerance that should be specified with a particular set of specified measurement tolerances, the maximum permissible measurement tolerances which should be specified to achieve a specified test result tolerance, and more consistent specified measurement tolerances.

1.4 These measurement and test result tolerances are not statistically determined tolerances that are obtained by using the test method but are the tolerances specified in the test method.

1.5 In the process of selecting test method tolerances, the task group developing or revising a test method must evaluate not only the consistency of the selected tolerances but also the technical and economical feasibility of the measurement tolerances and the suitability of the test result tolerance for the purposes for which the test method will be used. This practice provides guidance only for establishing the consistency of the test method tolerances.

1.6 This practice is presented in the following sections:

1.7 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 and health practices and determine the applicability of regulatory limitations prior to use.