THE QUALITY OF SURVEY DATA - TELEPHONE VERSUS FACE-TO-FACE INTERVIEWS

Those designing surveys and producing data have always been concerned about its quality. The increasing stringency of the financial constrai nts which affect public authorities and the increased scope of involve ment in the regulation of urban travel has led us to pay even greater attention to the quality of data. This issue is frequently covered in the literature on survey methods. However, comparisons between differe nt survey methods are more rarely conducted. The decision to conduct s uch an analysis is partly the result of the development of telephone u se to the detriment of other survey modes in many countries and also t he development of Computer-Aided Telephone Interviewing (CATI) which f acilitates the running and monitoring of the survey. This paper examin es several aspects of this question in order to compare the performanc e of telephone and face-to-face interviews. The first aspect is the re presentativeness of the sample, and therefore relates mainly to the is sue of nonresponses and the choice of a sample base. The second concer ns the accuracy of the information and involves the choice of a survey area and the recording of all trips, including short-distance travel. Finally, the quality of data is obviously determined by the quality o f the responses given by those interviewed. The answers we give freque ntly depend on the objective of the surveys, which leads us to put for ward a table which summarizes the performance of telephone and face-to -face interviews on the basis of the main objective of the survey. Bro adly, the telephone seems to be the favoured tool for surveys in the a rea of transport planning and surveys which aim to provide data for fo recasting models, mostly on the grounds of cost. However, face-to-face techniques are often preferred for surveys which aim to discover and analyze the factors which explain individual travel behaviour.