Elemental Considerations in Validity

Abstract

Validity is a term that is often invoked in decisions to use neuropsychological tests. Unfortunately, the context of this use is usually negative, as when a test is cited as invalid. The use of the term implies that a test can be determined to be either valid or invalid. Of course, most clinical neuropsychologists agree that a test that is “valid” for one population may be “invalid” for another. If this is true, can a test ever be evaluated as universally valid or invalid? A second question relates to how a test is evaluated as valid or invalid. This is a question of both method (How do we evaluate a test?) and of epistemology (How do we know what we know?). Although method may be discussed separately from epistemology, the obverse is not necessarily true. That is, how we know something is highly related to how we investigate that something. This chapter discusses general issues in the relationship between epistemology and method, and Chapter 5 discusses the methodological issues more directly.