The purposes of the present monograph are:(a) to celebrate the extension of the concept of validity as an indication that psychometrics is recognized as truly the handmaiden of psychology rather than merely of psychotechnology;(b) to argue that, since predictive, concurrent, and content validities are all essentially 6d hoc, construct validity is the whole of validity from a scientific point of view; 6(c) to analyze the components of construct validity, in particular proposing" structural component" as name for a previously only partly recognized aspect; and (d) to relate secular trends in test behavior to the validity problem. The presentation of these and related topics as a single monograph has an overriding purpose: to develop a coherent view of psychometrics, a mutually implicative test theory and method of test construction. Many current lines of research in psychometrics are discussed, either as contributing to or as contrasting with the present system. It would be unjust, however, to read the monograph as a review of psychometric literature. No attempt is made to evaluate any contribution or any line of work in toto, nor is inclusive coverage of current literature sought. If the exposition appears to claim that only the present view is admissible, that is an artifact of the argument, not an expression of belief or intention. CHAPTER I

EXTENSION OF THE CONCEPT OF VALIDITY Because of the difficulties to which the classical concept of validity led, there have been many attempts to modify and redefine validity in recent years, culminating in recognition that the new concept is essentially different from classical validity and requires an identifying name. The term constract validity was proposed by the APA Committee on Psychological Tests, which drew up the Technical Recommendations for Psy-