Practical Applications of Making a Common Ability Scale Using Item Response Theory

Abstract

A number of assessment tests for English，such as TOEFL or IELTS，describe examinees' ability on common score scales，which enable us to arrive at ability scores on a single scale regardless of the difficulty of test items. This article describes 1） a method of constructing a common scale in order to develop an item bank，2） a practical way to develop a computer adaptive test （CAT） system，and 3） a practical application of the Kyoto Institute of Technology （KIT） English speaking test. In order to make a common ability scale，it is necessary to employ item response theory （IRT） analysis to estimate the difficulty of item characteristics. When it comes to the practical application of a common scale，it is also necessary to utilize monitor examinees，who are administrated different kinds of test forms in order to equate ability scales. The procedure for making common scales enables us to administer different versions of parallel test forms in assessment programs..