Accuracy and confidence in group judgment

• Published in: Organizational behavior and human decision processes 1989-02, Vol.43 (1), p.1-28
• Main Authors: Sniezek, Janet A, Henry, Rebecca A
• Format: Article
• Language: English
• Subjects: Accuracy; Behavior. Attitude; Biological and medical sciences; Confidence; Fundamental and applied biological sciences. Psychology; Groups; Judgments; Organizational behavior; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Social psychology; Statistical analysis
• ISSN: 0749-5978; 1095-9920
• DOI: 10.1016/0749-5978(89)90055-1

A weighting scheme model is used to describe and evaluate the process by which groups combine individual judgments and their associated confidence levels into a single group judgment with some level of confidence. In general, the group judgment process is not well described as an averaging process. Group judgments were, with few exceptions, significantly more accurate than mean or median individual judgments, leading to a 23.7% reduction in standardized bias. Further, 30% of the group judgments were more accurate than the group's most accurate individual judgment. Two factors related to increased accuracy through grouping were (a) high disagreement, i.e., large variance, in initial judgments, and (b) group judgments outside the range of initial individual judgments. In addition to being more accurate, groups were generally more confident than individuals. Ratings of confidence and accuracy, but not 99% confidence interval size, were correlated with actual judgment accuracy. Limitations of the weighting scheme approach are discussed, with suggestions for further research on group judgments under uncertainty.