forecastingprinciples.com Reviews of Important Papers on Forecasting
Before 1985 Reviews
Review of:

David M. Boje and J. Keith Murnighan (1982), “Group confidence pressures in iterative decisions," Management Science, 28, 1187-1196.


In this study, individual estimates were compared with those from group face-to-face interaction and from groups with only written feedback. The experiment involved four estimation problems (two almanac questions and two on heights and weights of people). Participants were 324 undergraduates in group sizes of 3, 7, and 11. The confidence of group members went up over the three rounds in the Delphi-like procedure; this is a typical result. These gains in confidence were unrelated to accuracy; also not surprising. However, no gain was found in accuracy of the later rounds, which is mildly surprising in the light of previous research where small gains were found. Group members preferred the fact-to-face interaction and thought it the most effective; however, it was the least accurate; a finding that agrees with previous research. I enjoy studies with surprising results. Imagine, then, how pleased I was to find this conclusion in their study . . . 'group size had no significant effects on accuracy . . .'. This conclusion conflicts with research that dates back to Gordon (1924), and includes the more recent contributions by Huber and Delbecq (1972), Hogarth (1978) and Libby and Blashfield (1978).

References

Gordon, Kate (1924), "Group judgments in the field of lifted weights," Journal of Experimental Psychology , 7, 398-400.

Hogarth, Robin M. (1978), "A note on aggregating opinions," Organizational Behaviour and Human Performance , 21, 40-46.

Huber, George P. and Andre Delbecq (1972), "Guidelines for combining the judgments of individual members in decision conferences," Academy of Management Journal, 15, 161-174.

Libby, Robert and Roger K. Blashfield (1978), "Performance of a composite as a function of the number of judges, " Organizational Behavior and Human Performance, 21, 121-129.