It could be argued that one area that has produced some useful advances in educational psychology (amongst others) has been the use of better measurement of variables. Two aspects of this better measurement stand out. One involves the use of Rasch Measurement Models and the second involves developments in computer technology. Rasch measurement is relatively new. It was first worked out mathematically by George Rasch in the 1950s and published in 1960. Its use and development have been steadily growing and Rasch measurement is now on the point of producing a minor revolution in fields like educational psychology. Rasch measurement makes a striking advance on True Score Test Theory in a number of ways. What really brought the Rasch measurement revolution into focus were the advances in computer technology. This book, contains many papers that use linear measures of variables.