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In probability and statistics, an urn problem is an idealized mental exercise in which some objects of real interest (such as atoms, people, cars, etc.) are represented as colored balls in an urn or other container. One pretends to remove one or more balls from the urn; the goal is to determine the probability of drawing one color or another, or some other properties. A number of important variations are described below. An urn model is either a set of probabilities that describe events within an urn problem, or it is a probability distribution, or a family of such distributions, of random variables associated with urn problems.〔Dodge, Yadolah (2003) ''Oxford Dictionary of Statistical Terms'', OUP. ISBN 0-19-850994-4 〕 == Basic urn model == In this basic urn model in probability theory, the urn contains ''x'' white and ''y'' black balls, well-mixed together. One ball is drawn randomly from the urn and its color observed; it is then placed back in the urn (or not), and the selection process is repeated. Possible questions that can be answered in this model are: * Can I infer the proportion of white and black balls from ''n'' observations? With what degree of confidence? * Knowing ''x'' and ''y'', what is the probability of drawing a specific sequence (e.g. one white followed by one black)? * If I only observe ''n'' balls, how sure can I be that there are no black balls? (A variation on the first question) 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「urn problem」の詳細全文を読む スポンサード リンク
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