Georg William Rasch (/ˈræʃ/) (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.
He completed a master's degree in 1925 and received a doctorate in science with thesis director Niels Erik Nørlund in 1930.
His work in this field began when he used the Poisson distribution to model the number of errors made by students when reading texts.
At the same epoch, American scientists independently developed item response theory (IRT).