New Developments in Equivalence Testing
Ennis, D. M. and Ennis, J. M. (2008). IFPress, 11(4) 2-3.
Equivalence is a term used to describe a condition in which two items differ by less than some predetermined amount. Similar terms include bioequivalence, parity, equality and similarity. Bioequivalence is used in the context of drug effect differences while the term parity is often used in the context of consumer product differences. Equality has been used in a variety of contexts, including the recently reissued American Society for Testing and Materials (ASTM) claims guide, while it seems preferable to avoid using the term similarity as it has a different meaning altogether in the quantitative psychology literature. The ASTM claims guide distinguishes between two types of parity advertising claims, respectively termed equality and unsurpassed. An equality claim can be made when two products are essentially equivalent within some predetermined bounds on an attribute of interest. This means that the term equality could be misleading as it could be misunderstood to imply that there are no bounds involved in its definition. This is in spite of the fact that such bounds are required. In what follows we simplify and use the single term equivalence in place of all of the above application-specific terms.
Figure 1. Predetermined Bounds for Equivalence Testing