Georg Rasch was a Danish mathematician, statistician, and psychometrician, most famous for the development of a class of measurement models known as Rasch models.
Education
He studied with Resident Advisor Fisher and also briefly with Ragnar Frisch, and was elected a member of the International Statistical Institute in 1948. He completed a masters degree in 1925 and received a doctorate in science with thesis director Niels Erik Nørlund in 1930.
Career
In 1919, Rasch began studying mathematics at the University of Copenhagen. 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.
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. At the same epoch, American scientists independently developed item response theory (Item response theory).
Within Item response theory, 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).
Andersen, East. B. (1982) Georg Rasch (1901–1980), Psychometrika, 47,(4), 375-376.