A knowledgemeasuring ruler

– Measuring a child's growing knowledge should be comparable to measuring a child's increased height. The Rasch method aims to create the same kind of accuracy in the social sciences as in the natural sciences. A centimeter on a ruler is the same length regardless of where it is on the scale; similarly, the Rasch method creates a scoring system for things like reading ability that is exact.

As explained by David Andrich, professor of Education at the University of Western Australia.

GEORG RASCH (1901–1980) was a Danish mathematician, known for his method of measurement in which statistical models express the probability of a correct answer to a task as a function of the individual's ability and the difficulty of the task. It is a model that is used in education, mainly to measure development in both individuals and groups, says David Andrich, a world-leading expert on the Rasch method, who also used to work with Rasch himself.

– It is important to create a test that really measures what you want to investigate and nothing else. For example, you might want to know how much a fourth grader has developed his reading skills over the course of a year. Using the Rasch model, the test can be designed so that it measures the student's development, independent of other factors such as gender, age, background and so on. In order to do a good investigation, careful preliminary work is required. It could, for example, be about testing reading ability in several different ways or, if you instead want to use the method in the health field, to produce data about a patient's health and attitudes to care and treatment.

During a month-long stay in May, as visiting professor at the Department of Education and Special Education, David Andrich held a Rasch course and lectured on how the Rasch model can be used when assessing, among other things, school students' reading ability.