The Rasch model
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 with specific items related to product or service quality. In general, it is more difficult to measure satisfaction and quality levels of 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. Instead of deriving a 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 model is introduced from a theoretical perspective, listing relevant literature and websites. A discussion of Rasch models in practice is given, along with a detailed application to the ABC annual customer satisfaction survey. Software packages implementing the Rasch model are described.
14.1 An overview of the Rasch model
14.1.1 The origins and the properties of the model