The influence of verbal and non verbal language manipulations on data quality

The problems concerning data quality lead to negative consequences for transport planning; every year many millions of euros have been spent to collect data and on developing and using travel models that are based on these data. This paper is the result coming from studies about the effects of some different combinations languages, understanding that the early step for data quality is the questionnaire comprehension. It has been hypothesized and demonstrated that a number of verbal and non verbal languages and the visual presentation of response choices affect respondents’ perception and influence answers. Starting from this assumption, a research has been developed to test different forms of languages on a well defined group of people using a self-administered questionnaire. At this aim the university staff working in the department of transport and students attending transport courses have been chosen. The innovation in the design of the tests developed in the research is the use of a small group because each unit represents a reliable result concerning the people understanding of the question. The same questions, elaborated following different verbal and not verbal languages, have been proposed to the interviewed in the same time period to avoid that external effects influence the people answers. The results of this experiment are really interesting and suggest that differences in questions format influence the responses also for people with “high education” levels.