Combining Probability Forecasts: 60% and 60% Is 60%, but Likely and Likely Is Very Likely

• 成果类型: Article
• 署名作者: Mislavsky, Robert; Gaertig, Celia
• 署名单位: Johns Hopkins University; University of Chicago
• 刊物名称: MANAGEMENT SCIENCE
• ISSN/ISSBN: 0025-1909
• DOI: 10.1287/mnsc.2020.3902
• 发表日期: 2022
• 页码: 541-563
• 关键词: uncertainty; forecasting; verbal probabilities; combining judgments; combining forecasts; predictions

摘要

How do we combine others' probability forecasts? Prior research has shown that when advisors provide numeric probability forecasts, people typically average them (i.e., they move closer to the average advisor's forecast). However, what if the advisors say that an event is likely or probable? In eight studies (n = 7,334), we find that people are more likely to act as if they count verbal probabilities (i.e., they move closer to certainty than any individual advisor's forecast) than they are to count numeric probabilities. For example, when the advisors both say an event is likely, participants will say that it is very likely. This effect occurs for both probabilities above and below 50%, for hypothetical scenarios and real events, and when presenting the others' forecasts simultaneously or sequentially. We also show that this combination strategy carries over to subsequent consumer decisions that rely on advisors' likelihood judgments. We discuss and rule out several candidate mechanisms for our effect.