The Rasch Model
ABSTRACT This chapter introduces the Rasch model and its use, in the context of customer satisfaction surveys. The Rasch analysis provides effective measures of customer satisfaction from specific items related to product or service quality. In general, it is more difficult to measure satisfaction and quality levels from a service than it is for a product since a product's quality is directly observable and may be different from the level of satisfaction it provides. When dealing with a service, the perceived quality and level of customer satisfaction are the results of a complex process. The Rasch analysis supplies two sets of coefficients which provide a simultaneous evaluation of subjective features related to the degree of satisfaction and objective features related to intrinsic quality (Rasch, 1980). Instead of deriving a synthetic measurement of these two aspects, the Rasch model assigns a score to each individual and to each questionnaire item along a continuum. These scores make it possible to carry out an effective analysis of the survey responses. The first section in the chapter introduces the model from a theoretical perspective, listing relevant literature and web sites. Section 14.2 discusses Rasch models in practice with a detailed application to the ABC Annual Customer Satisfaction Survey. Section 14.3 describes software packages implementing the Rasch model. Section 14.4 summarises the chapter.