Consensus in the Delphi method: What makes a decision change?

Abstract

We examined whether giving feedback to participants in a Delphi study about the level of agreement across the expert panel had an effect on opinion change between rounds. We also considered the potential influence of participants' sociodemographic and professional characteristics. Five three-round Delphi studies were conducted independently, in which a total of 628 mental health experts responded to all three rounds. In each study, participants had to decide, based on their experience, whether a series of categories were relevant. The percentage of group agreement (i.e., percentage of participants who considered each category as relevant) in round 2 was shown as feedback in round 3, and responses in rounds 2 and 3 were considered to analyze opinion change. Results showed that when the feedback given in round 3 indicated that ≥75% of experts considered a category to be relevant, there was a further shift in opinion towards the group opinion (i.e., the category then yielded even greater consensus), whereas if the feedback indicated <75% group agreement, individual opinions tended to shift against the group opinion (i.e., consensus over the category decreased). Neither sociodemographic nor professional variables had a significant effect in explaining opinion shift. These results show that in Delphi studies, feedback has an influence on individual responses and the achievement of consensus.