Psychological measurement.

This paper analyzes the principle issues involved in the measurement of psychological variables along with various psychometric solutions to these problems. First, emphasis is placed on the difficulties that arise in psychological measurement due to the unique characteristics inherent in psychological events. These intrinsic limitations, however, were not an obstacle to the development of a rigorous empirical measurement tradition in psychology. This tradition originates in the psychophysical works of Weber and Fechner as well as the classical test theory formulated by Spearman. Moreover, two approaches to measurement theory, the classic one proposed by Stevens and the representational view, investigate the logic and foundations of measurement. This article pays special attention to the psychometric advances brought by Item Response Theory, which resolves some of the problems not appropriately solved within the framework of classical test theory. Item response theory serves as the basis for new technologies to build and assess psychological and educational tests. Finally, test validity and test use are discussed.