Tuesday, October 21, 2014

The effectiveness of Nominal, Delphi, and Interacting group decision making processes

By: Andrew H. Van de Ven and Andrew L. Delbecq

In their 1974 research, Van de Ven and Delbecq compared the effectiveness of nominal group technique (NGT), delphi technique, and traditional interacting group technique to identify which performed best in the decision making process.

NGT follows a process of first allowing members to silently, and on their own, generate a list of ideas and thoughts on how to answer the proposed problem.  Then, all of the members list their proposed solutions to the rest of the team.  All the responses are recorded and written out for the entire team to read.  Once all of the proposed solutions have been recorded, the team discusses each solution for its validity and to clarify what is meant by each solution.  Finally, the group independently votes on the solutions and the group's decision is derived from the outcome of the vote.

Interacting group technique is the widely used method of having team members have an unstructured discussion of the problem.  Participants propose solutions the group actively debates what the best course of action is.

Delphi allows for decision making when team members are not physically in the same location. The process used by Van de Ven and Delbecq began by issuing questionnaires by mail (today could be electronically) to participants who did not know the identify of any of the other participants.  Once the questionnaires were returned, the ideas generated where recorded and sent out in a second questionnaire that dove more in depth into the ideas.  Respondents voted on different solutions and returned the questionnaire.

Their study was conducted at a Midwestern university were students were asked to  define the job description of part-time student dormitory counselors.  The effectiveness of each technique was judged based on the quantity of unique ideas generated by the technique and the overall satisfaction of the outcome by the group.  They hypothesized that NGT would be more effective than delphi and delphi would be more effective than interacting.

The size of the groups was set to seven participants, which Van de Ven and Delbecq identified as about the size of many real world teams.  420 individuals were assigned to 60 heterogeneous groups, creating 20 groups for each of the three methods.

The results of the research found six main conclusions,

  1. No significant difference in the quantity of ideas generated by the NGT and Delphi groups
  2. Significantly more unique ideas were generated by delphi groups than interacting
  3. The highest difference in unique ideas was between NGT and interacting groups
  4. NGT groups had significantly greater satisfaction with the process than delphi
  5. NGT had a highly significant satisfaction with the process and interacting
  6. No significant difference in satisfaction between delphi and interacting


I am very pleased with the experimental design and result of Van de Ven and Delbecq's research.   I was suprised at fist as to why participants were more satisfied with NGT than with the delphi process.  The delphi process is a very impersonal process, where you don't know who the other participants are and lack the ability of the in-depth, back and fourth discussion that NGT provides.  I believe the lack of the social element does take away from the overall process.  The exit interview of the delphi participants stated the same answers.  The lack of social interaction can make participants feel less engaged in the process and lacked the ability to have an in depth discussion to clarify or develop new ideas.

Van De Ven, A. H and Delbecq, A. L. (1974).  The effectiveness of nominal, delphi, and interacting group decision making processes.  Academy of Management Journal. Pages 605 - 621.


  1. I find your study particularly interesting because it's used as a modifier rather than a method. Would you prefer to use it as a method or modifier?

    1. Kyle,

      I like the use of Delphi as a modifier. Much like Nominal Group Technique (NGT) it does appear to help produce better estimates and decisions. I much prefer the use of NGT due to the interaction between colleagues though. Just as the study showed, I believe it is a better technique that produces more and higher quality ideas and decisions.

  2. Harrison,

    As a student yourself, would you rather take part in NGT or a Delphi exercise?

  3. Joy,

    I much prefer the nominal group technique (NGT). I have never taken apart of a Delphi exercise so I cannot speak with experience with that technique. But I very much appreciate and believe in the value of communicating face to face. Also, if you are working with someone you have worked with in the past, you have may know the perspective that response is coming from. This allows you to have a deeper meaning of why something was said and generate even more ideas.