Rasch model's contribution to the study of items and item response scales formulation in opinion/perception questionnaires.

: Questionnaire-based inquiries make it possible to obtain data rather quickly and at relatively low cost, but a number of factors may influence respondents' answers and affect data's validity. Some of these factors are related to the individuals and the environment, while others are directly related to the characteristics of the questionnaire and its items: the text introducing the questionnaire, the order in which the items are presented, the number of responses categories and their labels on the proposed scale and the wording of items. The focus of this article is on this last point and its goal is to show how the developments of diagnostic features surrounding Rasch modelling can be used to study the impact of item wording in opinion/perception questionnaires on the responses obtained and on the location of anchor points of the item response scale.