Delphi questionnaires versus individual and group interviews: A comparison case

The article reports on a methodological investigation for different types of the communication device represented by the Delphi method. Traditionally mailed or computer-mediated questionnaires are used. The Delphi method was invented to overcome undesirable effects of group interaction while retaining the positive effects of interactive group judgments. This article supplies evidence for the opposite: the superiority of face-to-face techniques (individual and group interviews) as compared to mailed questionnaires in a three-round Policy Delphi using half-structured questionnaires. Moreover, the case study proves that they might produce different results. In a field- or quasi-experimental design the three techniques were compared for their effects. The performance of 100 panel members on a large number of quality standards in the Delphi method is described. A list of pros and cons of the three techniques in a (Policy) Delphi serves as a summary.