ASTM E2935-16

4.1 Laboratories conducting routine testing have a continuing need to make improvements in their testing processes. In these situations it must be demonstrated that any changes will not cause an undesirable shift in the test results from the current testing process nor substantially affect a performance characteristic of the test method. This standard provides guidance on experiments and statistical methods needed to demonstrate that the test results from a modified testing process are equivalent to those from the current testing process, where 4.1.1 Examples of modifications to the testing process include, but are not limited, to the following:

4.1.2 The equivalence limit, which represents a worst-case difference, is determined prior to the equivalence test and its value is usually set by consensus among subject-matter experts.

4.2 Two principal types of equivalence are covered in the practice, means equivalence and non-inferiority. Means equivalence implies that a sustained shift in test results between the modified and current testing processes refers to an absolute difference, meaning differences in either direction from zero. Non-inferiority is concerned with a difference only in the direction of an inferior outcome in a performance characteristic of the modified testing procedure versus the current testing procedure.

4.3 Risk Management—Guidance is also provided for determining the amount of data required to control the risks of making the wrong decision in accepting or rejecting equivalence (see Section X1.2).

1.1 This practice provides statistical methodology for conducting equivalence testing on numerical data from two sources to determine if their true means or variances differ by no more than predetermined limits.

1.2 Applications include (1) equivalence testing for bias against an accepted reference value, (2) determining means equivalence of two test methods, test apparatus, instruments, reagent sources, or operators within a laboratory or equivalence of two laboratories in a method transfer, and (3) determining non-inferiority of a modified test procedure versus a current test procedure with respect to a performance characteristic.

1.3 The guidance in this standard applies only to experiments conducted on a single material at a given level of the test result.

1.4 Guidance is given for determining the amount of data required for an equivalence trial. The control of risks associated with the equivalence decision is discussed.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 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.