Delphi Method Forecasting: Definition and How It's Used

Delphi Method

Xiaojie Liu / Investopedia

What Is the Delphi Method?

The Delphi method is a forecasting process and structured communication framework based on the results of multiple rounds of questionnaires sent to a panel of experts. After each round of questionnaires, the experts are presented with an aggregated summary of the last round, allowing each expert to adjust their answers according to the group response. This process combines the benefits of expert analysis with elements of the wisdom of crowds.

Key Takeaways

  • The Delphi method is a process used to arrive at a group opinion or decision by surveying a panel of experts.
  • Experts respond to several rounds of questionnaires, and the responses are aggregated and shared with the group after each round.
  • The experts can adjust their answers each round, based on how they interpret the “group response” provided to them.
  • The ultimate result is meant to be a true consensus of what the group thinks.

Understanding the Delphi Method

Several rounds of questionnaires are sent out to the group of experts, and the anonymous responses are aggregated and shared with the group after each round. The experts are allowed to adjust their answers in subsequent rounds, based on how they interpret the “group response” that has been provided to them. Since multiple rounds of questions are asked and the panel is told what the group thinks as a whole, the Delphi method seeks to reach the correct response through consensus.

The Delphi method was originally conceived in the 1950s by Olaf Helmer and Norman Dalkey of Rand Corp. The name refers to the Oracle of Delphi, a priestess at a temple of Apollo in ancient Greece known for her prophecies. The Delphi method allows experts to work toward a mutual agreement by conducting a circulating series of questionnaires and releasing related feedback to further the discussion with each subsequent round. The experts’ responses shift as rounds are completed based on the information brought forth by other experts participating in the analysis.

The Delphi method is a process of arriving at group consensus by providing experts with rounds of questionnaires, as well as the group response before each subsequent round.

Delphi Method Process

First, the group facilitator selects a group of experts based on the topic being examined. Once all participants are confirmed, each member of the group is sent a questionnaire with instructions to comment on each topic based on their personal opinion, experience, or previous research.

The questionnaires are returned to the facilitator, who groups the comments and prepares copies of the information. A copy of the compiled comments is sent to each participant, along with the opportunity to comment further. At the end of each comment session, all questionnaires are returned to the facilitator, who decides if another round is necessary or if the results are ready for publishing.

The questionnaire rounds can be repeated as many times as necessary to achieve a general sense of consensus.

Advantages of the Delphi Method

The Delphi method seeks to aggregate opinions from a diverse set of experts, and it can be done without having to bring everyone together for a physical meeting. Since the responses of the participants are anonymous, individual panelists don’t have to worry about repercussions for their opinions. The anonymity of the participants also helps prevent the “halo effect,” which sees higher priority given to the views of more powerful or higher-ranking members of the group.

By conducting Delphi studies, consensus can be reached over time as opinions are swayed, making the method very effective. In contrast with many other types of interviews and focus groups, Delphi studies allow participants to rethink and refine their opinions based on the input of others, contributing to a more reflective and thoughtful process.

Disadvantages of the Delphi Method

Although it provides the benefits of anonymity and the possibility for reevaluation and reflection, the Delphi method does not result in the same sort of interactions as a live discussion. A live discussion can sometimes produce a better example of consensus, as ideas and perceptions are introduced, broken down, and reassessed. Response times with the Delphi method can be long, which slows the rate of discussion. It is also possible that the information received back from the experts will provide no innate value.

The deliberate and drawn-out nature of the Delphi method also presents some challenges. Since the method often requires multiple rounds of questionnaires, there is a chance that some participants may drop out from the study before it has been completed. In addition, while there are benefits to giving participants the opportunity to reassess their views, there is a chance that they will adjust their responses so that they are more closely aligned with the views of the majority, reducing the diversity of opinions represented and diminishing the validity of the results.

What is the Delphi method used for?

The Delphi method is used to establish a consensus opinion about an issue or set of issues by seeking mutual agreement from a group of experts in the relevant field. The Delphi method has been used to conduct research in numerous areas, from the defense industry to healthcare.

How is the Delphi method conducted?

The group facilitator selects a group of experts based on the topic being examined and sends them a questionnaire with instructions to comment on each topic based on their personal opinion, experience, or previous research. The facilitator groups the comments from the returned questionnaires and sends copies to each participant, along with the opportunity to comment further. At the end of this session, the questionnaires are returned to the facilitator, who decides if another round is necessary or if the results are ready for publishing. This process can be repeated multiple times until a general sense of consensus is reached.

How is "consensus" defined when using the Delphi method?

Although the Delphi method seeks to pinpoint an area of mutual agreement among the pool of experts, it is unlikely that the participants will be in complete agreement on all issues—even after several rounds of questionnaires and opportunities for reassessment. Researchers applying the Delphi method may have different thresholds for exactly what constitutes a consensus, and some critics of the method point to the subjective nature of this determination as a shortcoming.

The Bottom Line

The Delphi method uses multiple rounds of questionnaires sent to a panel of experts to work toward a mutual agreement or consensus opinion. The participants modify their responses based on the information brought forth by other experts participating in the analysis. The Delphi method benefits from the anonymity of the participants and the opportunities it provides for reassessment, but it can also be time consuming and in some cases may be less effective than a live discussion or focus group.

Article Sources
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  1. Rand Corp. “An Experimental Application of the Delphi Method to the Use of Experts,” Pages 1–2 (Pages 11–12 of PDF).

  2. BMJ Journals, Evidence-Based Nursing. “What Are Delphi Studies?

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