Double checking the cross-check principle.

The cross-check principle was proposed by Jerger and Hayes over 20 years ago. Actually, the cross-check principle consists of a concept and a specific test protocol. The concept, that one test result confirms another test result, is still in use. Their specific protocol is essentially forgotten. The cross-check protocol they described, however, differs from more traditional test protocols. From the design of their cross-check protocol we can extract two unique testing strategies. The first strategy requires agreement between both tests before a decision can be made. This strategy can significantly improve testing performance; however, the "cost" of this strategy is a population of individuals for whom no decision is possible because the two tests disagree. The cross-check protocol uses a third test when the first two tests disagree. Essentially, the cross-check protocol employs an intermediate criterion, the second unusual strategy. Somewhat surprisingly, this intermediate criterion has the ability to simultaneously increase protocol hit rate and decrease protocol false alarm rate relative that of the individual tests in the protocol. The more traditional protocol criteria cannot do this. Each strategy offers some interesting and important advantages and should be considered by audiologists when using multiple tests.