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Open Access Open Badges Research article

An exploration of the use of simple statistics to measure consensus and stability in Delphi studies

Elizabeth A Holey1, Jennifer L Feeley2*, John Dixon1 and Vicki J Whittaker1

Author Affiliations

1 School of Health and Social Care, University of Teesside, Middlesbrough, TS1 3BA, UK

2 Department of Physiotherapy, Kings Mill Hospital, Mansfield Road, Sutton-In-Ashfield, Nottinghamshire, NG17 4JT, UK

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BMC Medical Research Methodology 2007, 7:52  doi:10.1186/1471-2288-7-52

Published: 29 November 2007



The criteria for stopping Delphi studies are often subjective. This study aimed to examine whether consensus and stability in the Delphi process can be ascertained by descriptive evaluation of trends in participants' views.


A three round email-based Delphi required participants (n = 12) to verify their level of agreement with 8 statements, write comments on each if they considered it necessary and rank the statements for importance. Each statement was analysed quantitatively by the percentage of agreement ratings, importance rankings and the amount of comments made for each statement, and qualitatively using thematic analysis. Importance rankings between rounds were compared by calculating Kappa values to observe trends in how the process impacts on subject's views.


Evolution of consensus was shown by increase in agreement percentages, convergence of range with standard deviations of importance ratings, and a decrease in the number of comments made. Stability was demonstrated by a trend of increasing Kappa values.


Following the original use of Delphi in social sciences, Delphi is suggested to be an effective way to gain and measure group consensus in healthcare. However, the proposed analytical process should be followed to ensure maximum validity of results in Delphi methodology for improved evidence of consensual decision-making.