A comparative study of differences in subjective likelihood estimates made by individuals, interacting groups, Delphi groups, and nominal groups

Abstract

This research evaluated four methods of eliciting subjective likelihood ratio estimates. The methods differed in terms of amount and structure of interaction permitted between estimators. These processes were individual estimates, and three group processes: a Talk-Estimate process approximating an interacting group, an Estimate-Feedback-Estimate process as an approximation of a Delphi group, an Estimate-Talk-Estimate process as combination of nominal and interacting groups. In this study the Estimate-Talk-Estimate group process was superior in approaching correct estimates in this judgmental task. This is consistent with the long research tradition which favors group as opposed to individual problem-solving in judgmental situations. The individual Estimate process and the Estimate-Feedback-Estimate technique performed about equally well with respect to both error and variability. If anything, written feedback appeared to lead to a reduction in the quality of estimates. Finally, the relatively poor results from the Talk-Estimate process are consistent with other studies which have pointed out dysfunctions of interacting group processes for judgmental tasks. © 1973.