Analysis of service quality: A comparison between scales using the Rasch model

The evaluation of service quality is as important as problematic matter. In fact, evaluation of the quality of a services involves all the difficulties one typically meets when try to measure an abstract concept: quality is an hidden, directly unobservable, meaning-needed aspect of a service. In this paper we consider a possible solution in efforts to measure quality, the use of Rasch Model (originally introduced in the psychometric field) in client satisfaction analysis. After a brief introduction to the Rasch model, this paper is focused on the effects of the measure scale used in collecting data on the results obtained. In particular, a data set in evaluating teachers' effectiveness in University courses is used to make comparison between two measure scales that differ in number of (ordinal) categories (five to four categories).