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In statistics, Fieller's theorem allows the calculation of a confidence interval for the ratio of two means. ==Approximate confidence interval== Variables ''a'' and ''b'' may be measured in different units, so there is no way to directly combine the standard errors as they may also be in different units. The most complete discussion of this is given by Fieller (1954). Fieller showed that if ''a'' and ''b'' are (possibly correlated) means of two samples with expectations and , and variances and and covariance , and if are all known, then a (1 − ''α'') confidence interval (''m''L, ''m''U) for is given by : where : Here is an unbiased estimator of based on r degrees of freedom, and is the -level deviate from the Student's t-distribution based on ''r'' degrees of freedom. Three features of this formula are important in this context: a) The expression inside the square root has to be positive, or else the resulting interval will be imaginary. b) When ''g'' is very close to 1, the confidence interval is infinite. c) When ''g'' is greater than 1, the overall divisor outside the square brackets is negative and the confidence interval is exclusive. 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「Fieller's theorem」の詳細全文を読む スポンサード リンク
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