For: psychometry For: psychrometrics

Psychometrics is the field of study concerned with the theory and technique of educational and psychological measurement, which includes the measurement of knowledge, abilities, attitudes, and personality traits. The field is primarily concerned with the study of measurement instruments such as questionnaires and tests. It involves two major research tasks, namely: (i) the construction of instruments and procedures for measurement; and (ii) the development and refinement of theoretical approaches to measurement.

Origins and background

Much of the early theoretical and applied work in psychometrics was undertaken in an attempt to measure intelligence. Francis Galton is often referred to as the father of psychometrics, having devised and included mental tests among his anthropometric measures. However, the origin of psychometrics also has connections to the related field of psychophysics. Two other pioneers of psychometrics obtained PhDs in the Leipzig Psychophysics Laboratory under Wilhelm Wundt; James McKeen Cattell in 1886 and Charles Spearman in 1906. The psychometrician L. L. Thurstone, founder and first President of the Psychometric Society in 1936, developed and applied a theoretical approach to the measurement referred to as the law of comparative judgment, an approach which has close connections to the psychophysical theory developed by Ernst Heinrich Weber and Gustav Fechner. In addition, Spearman and Thurstone both made important contributions to the theory and application of factor analysis, a statistical method that has been developed and used extensively in psychometrics.

More recently, psychometric theory has been applied in the measurement of personality, attitudes and beliefs, academic achievement, and in health-related fields. Measurement of these unobservable phenomena is difficult, and much of the research and accumulated art in this discipline has been developed in an attempt to properly define and quantify such phenomena. Critics, including practitioners in the physical sciences and social activists, have argued that such definition and quantification is impossibly difficult, and that such measurements are often misused, such as with psychometric personality tests used in employment procedures:

"For example, an employer wanting someone for a role requiring consistent attention to repetitive detail will probably not want to give that job to someone who is very creative and gets bored easily."

Figures who made significant contributions to psychometrics include Karl Pearson, L. L. Thurstone, Georg Rasch, Johnson O'Connor, Frederic M. Lord, Ledyard R. Tucker, and Arthur Jensen.

Definition of measurement in the social sciences

The definition of measurement in the social sciences has a long history. A currently widespread definition, proposed by Stanley Smith Stevens (1946), is that measurement is "the assignment of numerals to objects or events according to some rule". This definition was introduced in the paper in which Stevens proposed four levels of measurement. Although widely adopted, this definition differs in important respects from the more classical definition of measurement adopted throughout the physical sciences, which is that measurement is the numerical estimation and expression of the magnitude of one quantity relative to another (Michell, 1997). Indeed, Stevens' definition of measurement was put forward in response to the British Ferguson Committee, whose chair, A. Ferguson, was a physicist. The committee was appointed in 1932 by the British Association for the Advancement of Science to investigate the possibility of quantitatively estimating sensory events. Although its chair and other members were physicists, the committee also comprised several psychologists. The committee's report highlighted the importance of the definition of measurement. While Stevens' response was to propose a new definition, which has had considerable influence in the field, this was by no means the only response to the report. Another, notably different, response was to accept the classical definition, as reflected in the following statement: