ABSTRACT
This chapter is concerned with measurement validity, which refers to the correspondence between variations in the scores on a measure and variations among respondents on the underlying construct being assessed. Measurement validity presupposes measure reliability. It is focused on the adequacy of the measure representing the construct it is designed to assess. Types of measurement validity discussed in the chapter include, among others, face validity, content validity, criterion validity (concurrent validity and predictive validity), and convergent and discriminant validity. The latter two are evaluated in the multitrait-multimethod matrix (MTMM), which also is discussed and illustrated in the chapter. The central lesson of the MTMM, that the variance of measures consists of trait and method components is stressed, and this view is related back to classical measurement theory presented in Chapter 3.
Developing measures that meet the criteria of reliability in terms of internal consistency, temporal stability, or inter-observer agreement satisfies a basic requirement for the operationalization phase of a scientific investigation. In the first chapter of this text, however, we made a distinction between the adequacy of an operation in terms of replicability and its adequacy as a manifestation of a theoretical construct. This distinction marks the difference between the reliability of a measuring device and its validity. Whereas reliability has to do with the consistency of measurement, the validation of operations relative to the hypothetical concepts under investigation (constructs or latent factors) is crucial from the standpoint of theory development.
