Quantitative Psychology is the application of statistical and mathematical methods to the study of psychology. This area of study is loosely divided into the subfields of psychometrics and mathematical psychology. Psychometrics may be characterized as the application of statistical models to problems such as psychological scaling and test development, while mathematical psychology may be characterized as the development and testing of novel mathematical models that describe psychological processes.
Quantitative psychology is served by Division 5 of the American Psychological Association (Evaluation, Measurement and Statistics), which publishes the preeminent journal in the field, Psychological Methods.
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 differences between individuals and between groups of individuals. It involves two major research tasks, namely: the construction of instruments and procedures for measurement; and the development and refinement of theoretical approaches to measurement.
The first psychometric instruments were designed to measure the concept of intelligence. The best known historical approach involves the Stanford-Binet IQ test, developed originally by the French Psychologist Alfred Binet. Contrary to a fairly widespread misconception, there is no compelling evidence that it is possible to measure innate intelligence through such instruments, in the sense of an innate learning capacity unaffected by experience, nor was this the original intention when they were developed. Nevertheless, IQ tests are useful tools for various purposes. An alternative conception of intelligence is that cognitive capacities within individuals are a manifestation of a general component, or general intelligence factor, as well as cognitive capacity specific to a given domain.
Psychometrics is applied widely in educational assessment to measure abilities in domains such as reading, writing, and mathematics. The main approaches in applying tests in these domains have been Classical Test Theory and the more modern Item Response Theory and Rasch measurement models. These modern approaches permit joint scaling of persons and assessment items, which provides a basis for mapping of developmental continua by allowing descriptions of the skills displayed at various points along a continuum. Such approaches provide powerful information regarding the nature of developmental growth within various domains.
Mathematical Psychology is an approach to psychological research that is based on mathematical modeling. Such mathematical modeling allows to derive more exact hypotheses and, therefore, stricter empirical validations.
Mathematical psychology is closely related to psychometrics and statistics. The models used are mostly probabilistic but there are also discrete ones. It is used in many fields of psychology, especially in psychophysics, perception, cognitive psychology, and psychology of learning but also, e.g., in clinical psychology, social psychology, or psychology of music.
Central journals are the Journal of Mathematical Psychology and the British Journal of Mathematical and Statistical Psychology. There are two annual conferences in the field, the annual meeting of the Society for Mathematical Psychology in the U.S, and the annual European Mathematical Psychology Group (EMPG) meeting.