Psychometrics is a field of study within psychology concerned with the theory and technique of measurement. Psychometrics generally covers specialized fields within psychology and education devoted to testing, measurement, assessment, and related activities. Psychometrics is concerned with the objective measurement of latent constructs that cannot be directly observed. Examples of latent constructs include intelligence, introversion, mental disorders, and educational achievement. The levels of individuals on nonobservable latent variables are inferred through mathematical modeling based on what is observed from individuals' responses to items on tests and scales.
In psychometrics, item response theory (IRT) is a paradigm for the design, analysis, and scoring of tests, questionnaires, and similar instruments measuring abilities, attitudes, or other variables. It is a theory of testing based on the relationship between individuals' performances on a test item and the test takers' levels of performance on an overall measure of the ability that item was designed to measure. Several different statistical models are used to represent both item and test taker characteristics. Unlike simpler alternatives for creating scales and evaluating questionnaire responses, it does not assume that each item is equally difficult. This distinguishes IRT from, for instance, Likert scaling, in which "All items are assumed to be replications of each other or in other words items are considered to be parallel instruments". By contrast, item response theory treats the difficulty of each item as information to be incorporated in scaling items.
Louis Leon Thurstone was an American pioneer in the fields of psychometrics and psychophysics. He conceived the approach to measurement known as the law of comparative judgment, and is well known for his contributions to factor analysis. A Review of General Psychology survey, published in 2002, ranked Thurstone as the 88th most cited psychologist of the 20th century, tied with John Garcia, James J. Gibson, David Rumelhart, Margaret Floy Washburn, and Robert S. Woodworth.
In psychology and sociology, the Thurstone scale was the first formal technique to measure an attitude. It was developed by Louis Leon Thurstone in 1928, originally as a means of measuring attitudes towards religion. Today it is used to measure attitudes towards a wide variety of issues. The technique uses a number of statements about a particular issue, and each statement is given a numerical value indicating how favorable or unfavorable it is judged to be. These numerical values are prepared ahead of time by the researcher and not shown to the test subjects. The subjects then check each of the statements with which they agree, and a mean score of those statements' values is computed, indicating their attitude.
The Rasch model, named after Georg Rasch, is a psychometric model for analyzing categorical data, such as answers to questions on a reading assessment or questionnaire responses, as a function of the trade-off between the respondent's abilities, attitudes, or personality traits, and the item difficulty. For example, they may be used to estimate a student's reading ability or the extremity of a person's attitude to capital punishment from responses on a questionnaire. In addition to psychometrics and educational research, the Rasch model and its extensions are used in other areas, including the health profession, agriculture, and market research.
The polytomous Rasch model is generalization of the dichotomous Rasch model. It is a measurement model that has potential application in any context in which the objective is to measure a trait or ability through a process in which responses to items are scored with successive integers. For example, the model is applicable to the use of Likert scales, rating scales, and to educational assessment items for which successively higher integer scores are intended to indicate increasing levels of competence or attainment.
The law of comparative judgment was conceived by L. L. Thurstone. In modern-day terminology, it is more aptly described as a model that is used to obtain measurements from any process of pairwise comparison. Examples of such processes are the comparisons of perceived intensity of physical stimuli, such as the weights of objects, and comparisons of the extremity of an attitude expressed within statements, such as statements about capital punishment. The measurements represent how we perceive entities, rather than measurements of actual physical properties. This kind of measurement is the focus of psychometrics and psychophysics.
Georg William Rasch was a Danish mathematician, statistician, and psychometrician, most famous for the development of a class of measurement models known as Rasch models. He studied with R.A. Fisher and also briefly with Ragnar Frisch, and was elected a member of the International Statistical Institute in 1948.
The Academy of the Social Sciences in Australia (ASSA) is an independent, non-governmental organisation devoted to the advancement of knowledge and research in the social sciences. It has its origins in the Social Science Research Council of Australia, founded in 1942.
Patrick Colonel Suppes was an American philosopher who made significant contributions to philosophy of science, the theory of measurement, the foundations of quantum mechanics, decision theory, psychology and educational technology. He was the Lucie Stern Professor of Philosophy Emeritus at Stanford University and until January 2010 was the Director of the Education Program for Gifted Youth also at Stanford.
Malcolm Preston Skilbeck was an Australian educator who worked in educational policy analysis, curriculum, tertiary and secondary education, the teaching profession and educational innovation. Some of this work was done with the Organisation for Economic Co-operation and Development (OECD) and the United Nations Educational, Scientific and Cultural Organization (UNESCO).
A rating scale is a set of categories designed to elicit information about a quantitative or a qualitative attribute. In the social sciences, particularly psychology, common examples are the Likert response scale and 1-10 rating scales in which a person selects the number that is considered to reflect the perceived quality of a product.
David Reading Krathwohl was an American educational psychologist. He was the director of the Bureau of Educational Research at Michigan State University and was also a past president of the American Educational Research Association, where he served in multiple capacities, as a member of the research advisory committee for the Bureau of Research of the USOE and as regional chairman of the board of trusties of the Eastern Regional Institute for Education.
Stephen Webb Raudenbush is the Lewis-Sebring Professor of Sociology and Chairman of the Committee on Education at the University of Chicago. He is best known for his development and application of hierarchical linear models (HLM) in the field of education but he has also published on other subjects such as health and crime. Hierarchical linear models, which go by many other names, are used to study many natural processes. To use an example from education, a three level hierarchical model might account for the fact that students are nested in classrooms which are nested in schools. With the right data one could go further and note that schools are nested in districts which are nested in states. Repeated measures of the same individuals can be studied with these models as observations nested in people.
Psychometric software is software that is used for psychometric analysis of data from tests, questionnaires, or inventories reflecting latent psychoeducational variables. While some psychometric analyses can be performed with standard statistical software like SPSS, most analyses require specialized tools.
Benjamin Drake Wright was an American psychometrician. He is largely responsible for the widespread adoption of Georg Rasch's measurement principles and models. In the wake of what Rasch referred to as Wright's “almost unbelievable activity in this field” in the period from 1960 to 1972, Rasch's ideas entered the mainstream in high-stakes testing, professional certification and licensure examinations, and in research employing tests, and surveys and assessments across a range of fields. Wright's seminal contributions to measurement continued until 2001, and included articulation of philosophical principles, production of practical results and applications, software development, development of estimation methods and model fit statistics, vigorous support for students and colleagues, and the founding of professional societies and new publications.
Bryan Stanley Turner is a British and Australian sociologist. He was born in January 1945 in Birmingham, England. Turner has held university appointments in England, Scotland, Australia, Germany, Holland, Singapore and the United States. He was a Professor of Sociology at the University of Cambridge (1998–2005) and Research Team Leader for the Religion Cluster at the Asian Research Institute, National University of Singapore (2005–2008).
Anton K. Formann was an Austrian research psychologist, statistician, and psychometrician. He is renowned for his contributions to item response theory, latent class analysis, the measurement of change, mixture models, categorical data analysis, and quantitative methods for research synthesis (meta-analysis).
Gideon Jan (Don) Mellenbergh was a Dutch psychologist, who was Professor of Psychological methods at the University of Amsterdam, known for his contribution in the field of psychometrics, and Social Research Methodology.
Robert Andrew Wilson is an Australian philosopher who has worked in Canada, the United States, and Australia. He has been professor of philosophy at the University of Western Australia since November 2019, after teaching previously at La Trobe University (2017-2019), the University of Alberta, the University of Illinois, Urbana-Champaign (1996–2001), where he was a member of the Cognitive Science Group at the Beckman Institute for Advanced Science and Technology, and at Queen's University (1992–1996).
