Abstract

How does one scientifically verify a psychometric instrument designed to assess the mental competence of medical patients who are asked to consent to medical treatment? Aside from satisfying technical requirements like statistical reliability, results yielded by such a test must conform to at least some accepted pretheoretical desiderata; for example, determinations of competence, as measured by the test, must capture a minimal core of accepted basic intuitions about what competence means and what a theory of competence is supposed to do. The concepts of “face validity” and “content validity” are both important here. Face validity “indicates that an instrument appears to test what it is supposed to and that it is a plausible method for doing so” (Portney and Watkins 2000, 82). Content validity “means that the test contains all the elements that reflect the variable being studied” (Portney and..