Delphi method

A systematic, interactive forecasting method which relies on sequential questionnaires completed by carefully chosen groups of experts. It is frequently used in forecasting, foresight,, and policy studies. In a sense, the Delphi method is a controlled debate. The reasons for extreme opinions are made explicit. More often than not, groups of experts move toward consensus; but even when this does not occur, the reasons for disparate positions become clear. Planners reviewing this material can make judgments based on these reasons and their own knowledge and goals. Because the number of respondents is usually small, studies using the Delphi method do not (and are not intended to) produce statistically significant results; in other words, the results provided by any panel do not predict the response of a larger population or even a different Delphi panel. They represent the synthesis of opinion of the particular group, no more, no less. The value of the Delphi method rests with the ideas it generates, both those that evoke consensus and those that do not. The arguments for the extreme positions also represent a useful product. Questions included in a Delphi may be of any sort that involves judgment, including, for example, the size of a future market, whether or not the CEO should receive a raise, or the proper policy to achieve a goal. In planning applications, the questions generally are of three types. Forecasts of the occurrence of future developments. Forecasts of future developments call for answers about when an event is expected to occur or about the future value of some parameter; desirability of some future state. Questions dealing with desirability ask for judgments about whether an event ought to occur, and the basis for the recommendation; and the means for achieving or avoiding a future state. Questions dealing with policy involve the traditional reporter's questions about implementation: who, what, when, where, and how much, and, of course, the likelihood that any policy will, in fact, accomplish its intended goals. These three types of questions may require different kinds of experts. The likelihood questions may involve hands-on experience and intimate knowledge of the frontiers of research. The desirability questions may involve a moral, political, or social dimension quite distinct from the disciplinary expertise involved in judging likelihood. The policy question may involve knowledge of the art of the possible. The Delphi method was designed to encourage a true debate through questionnaires, independent of personalities. Questions are usually formulated as hypotheses, and experts state the time or other factors associated with these hypotheses. Each round of questioning is followed by feedback from the preceding round of replies, usually presented anonymously. The experts are encouraged to revise their earlier answers in light of the replies of other members of the group. Two key attributes of a Delphi study are: feedback and anonymity of the respondents. After several rounds the process is complete and the median scores determine the final answers. One cannot attach a statistical significance to the results; the primary strength of Delphi is its ability to explore, coolly and objectively, issues that require judgment. Two main weaknesses of Delphi are: 1) the ease with which questions can be asked for which better techniques exist. 2) The time that it takes. A single round can easily require three weeks; a three-round Delphi is at least a three- to four-month affair, including subjective and analysis time. However, a Real-time Delphi system is in existence that allows a rapid on-line sequence of cycles, so that a whole project can be completed in a few weeks.