Indices of Discrimination or Diagnostic Accuracy
Subjects in experiments on perception, learning, memory, and cognition are often required to make a series of fine discriminations. In a common method, a single stimulus is presented on each trial and the subject indicates which of two similar stimuli it is, or from which of two similar categories of stimuli it was drawn. In addition, in several practical settings, professional diagnosticians and prognosticators must say time and again which of two conditions, confusable at the moment of decision, exists or will exist. Among them are physicians, non destructive testers, product inspectors, process-plant supervisors, weather fore casters, mineralogists, stockbrokers, librarians, survey researchers, and admis sions officers. There is interest in knowing both how accurately the experimental subjects and professionals perform and how accurately their various tools per form, and a dozen or more indices of discrimination accuracy are in common use. In this chapter I cover a way of discriminating among those indices that permits sifting the ones that are valid and reliable from the ones that are not. This proposed touchstone for indices is the relative (or receiver) operating charac teristic (ROC).