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What is the Delphi Study Technique?

Updated: Mar 5, 2020

The Delphi technique is a process for consensus-building by using a series of questionnaires to collect data from a panel of selected experts (Dalkey & Helmer, 1963; Dalkey, 1969; Linstone & Turoff, 1975; Lindeman, 1981; Martino, 1983; Young & Jamieson, 2001). The responses of experts to a first questionnaire are combined. Another questionnaire is sent out with feedback from the first questionnaire and so on until a consensus among experts is obtained (Powell, 2003). The researcher selects and defines what the term expert specifically relates to in the study. There should be a precise description of what constitutes expertise and the sampling method for selecting experts (Jorm, 2015, para. 20). The size of the expert panel can vary but finding will be more stable with larger panels (Jorm, 2015). For example, if the panel is composed of ten experts then one individual's response will account for 10 percent which can influence finding significantly. Okoli and Pawlowski (2004) recommend a panel of between 10 and 18 experts.

There are several key elements to the Delphi method: firstly, a facilitator organizes the Delphi study and recruits a group with expertise on the topic, a questionnaire is created with statements that the experts rate based on their agreement, responses are gathered, feedback is given to the group related to their responses, members revise their responses and eventually converge with statistical criteria used to define consensus (Jorm, 2015, para. 15). In The Wisdom of Crowds, Surowiecki (2004) discusses the process of systematically and methodically using consensus, a collection of similar answers sourced from multiple individuals, to produce accurate outcomes. Surowiecki (2004) expands on specific conditions that must be met to utilize a consensus properly: diversity of expertise, independence, decentralization, and aggregation (Jorm, 2015, para. 12). Independence is particularly important since researchers must avoid the group-think phenomenon that occurs due to group pressures and leads to irrational decisions (Jorm, 2015, para. 11).The Delphi method is an excellent tool to glean valuable data from experienced individuals on subjects that are challenging to quantify traditionally.


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Linstone, H. A., & Turoff, M. (1975). Introduction. In H. A. Linstone, & M. Turoff (Eds.). The Delphi method: Techniques and applications. Reading, MA: Addison-Wesley Publishing Company. pp. 3-12

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Okoli, C. and Pawlowski, S. (2004). The Delphi method as a research tool: An example, design considerations and applications. Information & Management, 42(1): 15–29.

Powel, C. (2003). Early indicators of child abuse and neglect: A multi-professional Delphi study. Wiley InterScience, 12(1): 25–40.

Surowiecki, J. (2004). The Wisdom of Crowds: Why the Many Are Smarter Than the Few. London: Abacus.

Toepoel, V., & Emerson, H. (2017). Using experts’ consensus (the Delphi method) to evaluate weighting techniques in web surveys not based on probability schemes. Mathematical Population Studies, 24(3), 161–171.

Young, S. J., & Jamieson, L. M. (2001). Delivery methodology of the Delphi: A comparison of two approaches. Journal of Park and Recreation Administration, 19 (1), 42-58.