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The Bradley–Terry model is a probability model that can predict the outcome of a comparison. Given a pair of individuals and drawn from some population, it estimates the probability that the pairwise comparison turns out true, as : where is a positive real-valued score assigned to individual . The comparison can be read as " is preferred to ", " ranks higher than ", or " beats ", depending on the application. For example, may represent the skill of a team in a sports tournament, estimated from the number of times has won a match. then represents the probability that will win a match against .〔〔 Another example used to explain the model's purpose is that of scoring products in a certain category by quality. While it's hard for a person to draft a direct ranking of (many) brands of wine, it may be feasible to compare a sample of pairs of wines and say, for each pair, which one is better. The Bradley–Terry model can then be used to derive a full ranking.〔 == History and applications == The model is named after R. A. Bradley and M. E. Terry, who presented it in 1952, although it had already been studied by Zermelo in the 1920s. Real-world applications of the model include estimation of the influence of statistical journals, or ranking documents by relevance in machine-learned search engines. In the latter application, may reflect that document is more relevant to the user's query than document , so it should be displayed earlier in the results list. The individual then express the relevance of the document, and can be estimated from the frequency with which users click particular "hits" when presented with a result list. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bradley–Terry model」の詳細全文を読む スポンサード リンク
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