Last update:
02-Aug-2018

The Delphi method is a consensus method that aims to find general agreement among an expert panel on a specific research topic. The selection and sampling method of the experts should be explicit and clear, and should be defined prior to the study. The research question of a study defines the selection of the experts, with health professionals being the most frequent choice. In a Delphi study, first, one researcher is assigned as the facilitator, to organize an expert panel and undertake communication with the experts. In the first round of the study, the initial questionnaire is distributed to the expert panel for the assessment by the members. The participating experts assess the importance of each item of the questionnaire using, usually, a nine-point Likert scale or less frequently, a seven-point, five-point or three-point Likert scale. The researchers analyze the first round data and construct a second round questionnaire that includes the items that did not achieve consensus in the first round, along with new items that arose from the comments of the experts on the first round. Specifically, the researchers include in the final questionnaire those items that were considered by the experts to be important in the first round, using predefined statistical criteria. During the second round, the facilitator informs each expert, anonymously, about the degree of consensus between his(her) answers and the answers of the other experts. Each expert can thus reconsider his(her) answers on common items between the first and the second round questionnaires, knowing the answers of the other experts. The Delphi study design includes the following issues: Τhe research question, selection of the experts, the number of the experts, construction of the questionnaire, the information provided to experts and administration of the questionnaire.

Key words: Consensus method, Delphi method, Expert, Likert scale, Questionnaire.