Delphi method

The Delphi method, or Delphi technique ( ; also known as Estimate–Talk–Estimate, or ETE), is a structured communication technique, or method, originally developed as a systematic, interactive forecasting method that relies on a panel of experts. Delphi has been widely used for business forecasting and has certain advantages over another structured forecasting approach, prediction markets.

Delphi can also be used to help reach expert consensus and develop professional guidelines. It is used for such purposes in many health-related fields, including clinical medicine, public health, and research.

Delphi is based on the principle that forecasts (or decisions) from a structured group of individuals are more accurate than those from unstructured groups. In classic applications, experts answer questionnaires in two or more discrete rounds. However, modern Real-Time Delphi formats often utilize a continuous, roundless interaction. After each round, a facilitator, or change agent, provides an anonymised summary of the experts' forecasts from the previous round as well as the reasons they provided for their judgments. Thus, experts are encouraged to revise their earlier answers in light of the replies of other members of their panel. It is believed that during this process the range of the answers will decrease and the group will converge towards the "correct" answer. Finally, the process is stopped after a predefined stopping criterion (e.g., number of rounds, achievement of consensus, stability of results), while traditional stopping criteria aimed for statistical convergence (e.g., mean or median scores), contemporary methodology prioritizes mapping the landscape of expert opinion, exploring qualitative reasoning, and identifying valid minority views rather than forcing an artificial consensus.

Special attention has to be paid to the formulation of the Delphi theses and the definition and selection of the experts in order to avoid methodological weaknesses that severely threaten the validity and reliability of the results. For example, care must be taken to ensure that the panelists have the requisite subject-matter expertise and that the more domineering participants do not overwhelm weaker-willed participants—the former may be less inclined to change their minds, or the latter more motivated to fit in, and either case could inhibit reaching true consensus.