Headline: The Group Delphi Process in the Social and Health Sciences

The group Delphi method is a Delphi variant in which the anonymity of the experts is abandoned in favour of an open exchange among professinals. The experts are invited to a joint workshop and evaluate a standardized questionnaire in successive small groups with rotating composition. Through the open exchange, arguments for the evaluations are revealed and one can test (i) whether divergent judgements can be resolved argumentatively or semantically or (ii) whether there is an agreement about an unresolved dissent (consensus on dissent). At the end of the group Delphi workshop, there is usually a much clearer distribution of judgements and substantive justifications for each of the prevailing judgements. The group Delphi method thus facilitates a quantitative and qualitative improvement in knowledge. For the health sciences, the method is particularly suitable for inter- and transdisciplinary consensus-finding on the effectiveness of diagnostic or therapeutic advances, as an evaluation instrument for various strategies, and for the discursive investigation of social or transformation processes that are appropriate for specific settings. The application for a group Delphi relies clearly on a defined research question the answering of which requires methodological expertise. However, compared to other Delphi variants, ithe group Delphi has been used rather rarely so far.