GEORG RASCH (21 September 1901 – 19 October 1980) 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.

In 1919, Rasch began studying mathematics at the University of
Copenhagen . He completed a master's degree in 1925 and received a
doctorate in science with thesis director
**Niels Erik Nørlund** 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.

CONTENTS

* 1 Contributions to psychometrics
* 2 Major publications
* 3 Obituary
* 4 References
* 5 External links

CONTRIBUTIONS TO PSYCHOMETRICS

**Georg Rasch** is best known for his contributions to psychometrics. His
work in this field began when he used the
**Poisson distribution** to
model the number of errors made by students when reading texts. He
referred to the model as the multiplicative Poisson model.

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.

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.

OBITUARY

Andersen, E. B. (1982)
**Georg Rasch** (1901–1980), Psychometrika,
47,(4), 375-376.

REFERENCES

* ^
**Georg Rasch** at the Mathematics Genealogy Project