Measuring Personality and Psychopathology

Contemporary scale construction methods focus heavily on a construct validation approach that elaborates the extent to which a measure can be said to reflect a theoretical (and hence not directly observable) construct. The construct validation approach emphasizes the interplay between the theoretical elaboration of the construct and its methodological validation. Three stages define, in general, the development of a scale using the construct validation approach. The stage of theory formulation involves an explication of the content domain of the construct, a delineation of the nature of the classification model and the linkages between constructs in the model, and a specification of the relationship of constructs to external variables, such as etiology or treatment outcome. The second stage of internal validation involves the operationalization of the constructs and examining various internal properties of the classification, such as interrater reliability, stability of measurement over occasions, internal correlation matrices, or the replicability of classification or factorial structures across different samples. The third stage of construct validation involves external validation. At this stage, links of the constructs to other variables related to etiology, course, or prediction must be tested. This process involves both convergent and discriminant validation. This chapter surveys important issues and procedures in the construction and implementation of measures of personality and psychopathology. Specific issues at each stage of scale development are discussed, and the methods of the construct validation approach are contrasted with other scale construction methods. Keywords: inventory; measurement; personality; psychometric; psychopathology; scale; test construction; test development