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In a methodological experiment, carried out within the framework of the Swiss Household Panel, two data collection strategies were evaluated: Computer Assisted Personal Interviews (CAPI) and Computer Assisted Telephone Interviews (CATI). The study was designed as a split-ballot in combination with repeated measurements. The participation rates in the two modes were similar and most answer distributions were the same in both modes. Moreover, it is shown that CATI saves costs and time in comparison with CAPI. Using a Multitrait- Multimethod design, estimates of reliability and validity were obtained for all data. Comparing these estimates, the conclusion must be that the choice of CATI versus CAPI has no implications for the quality of the data. Once the choice has been made, it does not make a very large difference either which type of response scale is used. What can really make a difference are the formulation and the topic of the question.
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