Face-to-face interviews and telephone surveys as complementary research methods

Most social surveys in Spain use face-to-face in order to collect data. However, in market research telephone survey is the most prevalent mode. But the cost of achieving a survey using both traditional modes is increasing and, at the same time, the response rates decrease. Because each mode has its own weaknesses and strengths, the idea of mixing modes of data collection is becoming more and more popular. Nevertheless, combining different modes of data collection may be problematic if people answer differently depending on the mode. This paper presents findings from an experimental study carried out in Spain to assess the impact a change in data collection mode from the current face-to-face interviewing to telephone might have on data quality and to study the likely causes of any observed mode effects.