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The recently reissued ASTM Claims Guide provides a useful classification of types of claims and recommendations concerning appropriate product testing. Figure 1 is a schematic summary of the claims discussed in that document. There are comparative and non-comparative claims. The comparative group includes superiority and parity claims. The guide separates parity claims into two types – equality and unsurpassed. An equality claim is justified when two products are essentially equivalent within some reasonably defined bounds on an attribute of interest. A product is unsurpassed when it exceeds the lower bound for equality. According to this definition, an unsurpassed claim can be made when a product meets the equality requirement or is superior. The guide provides the statistical tools to support an unsurpassed claim, but not an equality claim. In this report we will discuss both of these types of parity claims.
Figure 1. Schematic depiction of the ASTM Claims Guide classification.