Georg Rasch
Encyclopedia
Georg Rasch was a Danish mathematician
, statistician
, and psychometrician
, most famous for the development of a class of measurement
models known as Rasch model
s. He studied with R.A. Fisher
and also briefly with Ragnar Frisch, and was elected a member of the International Statistical Institute
in 1948.
In 1919, Rasch began studying mathematics at the University of Copenhagen
. He completed a masters degree in 1925 and received a doctorate in science in 1930. Rasch married in 1928. Unable to find work as a mathematician in the 1930s, he turned to work as a statistical consultant. In this capacity he worked on a range of problems, including problems of biological growth.
to model the number of errors made by students when reading texts. He referred to the model as the multiplicative Poisson model.
Prominent advocates of Rasch's models including Benjamin Wright and David Andrich
, both having made substantial contributions to the theory and application of Rasch's models. David Andrich spent six months during 1977 as a fellow of the Danish Institute for Educational Research working with Georg Rasch.
He later developed the Rasch model
for dichotomous data, which he applied to response data derived from intelligence and attainment tests including data collected by the Danish military. At the same epoch, American
scientists independently developed item response theory
(IRT). Within IRT, the Rasch model is one of the most simple response models. In contrast to other simple models, the Rasch model has a distinctive mathematical property: the model parameters (item difficulties, examinee ability) are sufficient statistics. Rasch demonstrated that his approach met criteria for measurement deduced from an analysis of measurement in the physical sciences. He also proposed generalizations of his model (Rasch, 1960/1980, 1977).
Today, the Rasch model is used extensively in assessment in education and educational psychology
, particularly for attainment and cognitive assessments.
Rasch, G. (1961). On general laws and the meaning of measurement in psychology, pp. 321–334 in Proceedings of the Fourth Berkeley Symposium on Mathematical Statistics and Probability, IV. Berkeley: University of Chicago Press, 1980.
Rasch, G. (1977). On Specific Objectivity: An attempt at formalizing the request for generality and validity of scientific statements. The Danish Yearbook of Philosophy, 14, 58-93.
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
, statistician
Statistician
A statistician is someone who works with theoretical or applied statistics. The profession exists in both the private and public sectors. The core of that work is to measure, interpret, and describe the world and human activity patterns within it...
, and psychometrician
Psychometrics
Psychometrics is the field of study concerned with the theory and technique of psychological measurement, which includes the measurement of knowledge, abilities, attitudes, personality traits, and educational measurement...
, most famous for the development of a class of measurement
Measurement
Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as the metre, second or degree Celsius...
models known as Rasch model
Rasch model
Rasch models are used for analysing data from assessments to measure variables such as abilities, attitudes, and personality traits. For example, they may be used to estimate a student's reading ability from answers to questions on a reading assessment, or the extremity of a person's attitude to...
s. He studied with R.A. Fisher
Ronald Fisher
Sir Ronald Aylmer Fisher FRS was an English statistician, evolutionary biologist, eugenicist and geneticist. Among other things, Fisher is well known for his contributions to statistics by creating Fisher's exact test and Fisher's equation...
and also briefly with Ragnar Frisch, and was elected a member of the International Statistical Institute
International Statistical Institute
The International Statistical Institute is a professional association of statisticians. The Institut International de Statistique or International Statistical Institute was founded in 1885 although there had been international congresses from 1853.. The Institute publishes a variety of books and...
in 1948.
In 1919, Rasch began studying mathematics at the University of Copenhagen
University of Copenhagen
The University of Copenhagen is the oldest and largest university and research institution in Denmark. Founded in 1479, it has more than 37,000 students, the majority of whom are female , and more than 7,000 employees. The university has several campuses located in and around Copenhagen, with the...
. He completed a masters degree in 1925 and received a doctorate in science in 1930. Rasch married in 1928. Unable to find work as a mathematician in the 1930s, he turned to work as a statistical consultant. In this capacity he worked on a range of problems, including problems of biological growth.
Contributions to psychometrics
Georg Rasch is best known for his contributions to psychometrics. His work in this field began when he used the Poisson distributionPoisson distribution
In probability theory and statistics, the Poisson distribution is a discrete probability distribution that expresses the probability of a given number of events occurring in a fixed interval of time and/or space if these events occur with a known average rate and independently of the time since...
to model the number of errors made by students when reading texts. He referred to the model as the multiplicative Poisson model.
Prominent advocates of Rasch's models including Benjamin Wright and David Andrich
David Andrich
David Andrich has made substantial contributions to quantitative social science including seminal work on the Polytomous Rasch model for measurement, which is used in the social sciences, in health and other areas. He is currently a Winthrop Professor at the University of Western Australia, where...
, both having made substantial contributions to the theory and application of Rasch's models. David Andrich spent six months during 1977 as a fellow of the Danish Institute for Educational Research working with Georg Rasch.
He later developed the Rasch model
Rasch model
Rasch models are used for analysing data from assessments to measure variables such as abilities, attitudes, and personality traits. For example, they may be used to estimate a student's reading ability from answers to questions on a reading assessment, or the extremity of a person's attitude to...
for dichotomous data, which he applied to response data derived from intelligence and attainment tests including data collected by the Danish military. At the same epoch, American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
scientists independently developed item response theory
Item response theory
In psychometrics, item response theory also known as latent trait theory, strong true score theory, or modern mental test theory, is a paradigm for the design, analysis, and scoring of tests, questionnaires, and similar instruments measuring abilities, attitudes, or other variables. It is based...
(IRT). Within IRT, the Rasch model is one of the most simple response models. In contrast to other simple models, the Rasch model has a distinctive mathematical property: the model parameters (item difficulties, examinee ability) are sufficient statistics. Rasch demonstrated that his approach met criteria for measurement deduced from an analysis of measurement in the physical sciences. He also proposed generalizations of his model (Rasch, 1960/1980, 1977).
Today, the Rasch model is used extensively in assessment in education and educational psychology
Educational psychology
Educational psychology is the study of how humans learn in educational settings, the effectiveness of educational interventions, the psychology of teaching, and the social psychology of schools as organizations. Educational psychology is concerned with how students learn and develop, often focusing...
, particularly for attainment and cognitive assessments.
Major publications
Rasch, G. (1960/1980). Probabilistic models for some intelligence and attainment tests.(Copenhagen, Danish Institute for Educational Research), expanded edition (1980) with foreword and afterword by B.D. Wright. Chicago: The University of Chicago Press.Rasch, G. (1961). On general laws and the meaning of measurement in psychology, pp. 321–334 in Proceedings of the Fourth Berkeley Symposium on Mathematical Statistics and Probability, IV. Berkeley: University of Chicago Press, 1980.
Rasch, G. (1977). On Specific Objectivity: An attempt at formalizing the request for generality and validity of scientific statements. The Danish Yearbook of Philosophy, 14, 58-93.
External links
- Lina Wøhlk Olsen, Essays on Georg Rasch and his contributions to statistics, PhD thesis Univ. of Copenhagen, in part online here, in part published elsewhere.
- Institute for Objective Measurement - some Georg Rasch papers online here