2.1.3. Delphi Method

Some authors mark the Delphi method as one of the first formal elicitation approaches of structured expert judgments [16] dating back to the 1950–60s. By applying a structured questionnaire, the experts are asked remotely, individually and anonymously/confidentially for their responses. After that, their answers are collated [16,24] (while removing the 25% upper and 25% lower responses in some cases [16]). In a second round, selected questions are sent back to the DMs for them to review and eventually correct their initial evaluations. This is repeated until the expert group reaches consensus [16,24].

The outlined advantages of the Delphi technique include the avoidance of group biases common for personal meetings as well as the participation of larger expert panel through the remote inquiries [24]. The main drawbacks pointed out are the time-consuming character [24], possible questionnaire ambiguity and the possible alteration of the responses before the next evaluation round [16].
