Georg Rasch

Georg William Rasch (1901 to 1980) was a Danish mathematician, statistician and psychometrician, best known for the family of measurement models that carry his name. He began studying mathematics at the University of Copenhagen in 1919, took a master degree in 1925 and a doctorate in science in 1930 under Niels Erik Nørlund. Unable to find work as a mathematician in the 1930s he became a statistical consultant, working on problems such as biological growth. He studied with R. A. Fisher and briefly with Ragnar Frisch, and was elected to the International Statistical Institute in 1948. His psychometric work began with a multiplicative Poisson model of reading errors and led to the Rasch model for dichotomous data, whose parameters are sufficient statistics. The model is now widely used in educational and psychological assessment.