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| mean =| median =| mode =| variance =| skewness =| kurtosis =| entropy =| mgf =| char =| }} In probability theory and statistics, the zeta distribution is a discrete probability distribution. If ''X'' is a zeta-distributed random variable with parameter ''s'', then the probability that ''X'' takes the integer value ''k'' is given by the probability mass function : where ζ(''s'') is the Riemann zeta function (which is undefined for ''s'' = 1). The multiplicities of distinct prime factors of ''X'' are independent random variables. The Riemann zeta function being the sum of all terms for positive integer ''k'', it appears thus as the normalization of the Zipf distribution. Indeed the terms "Zipf distribution" and the "zeta distribution" are often used interchangeably. But note that while the Zeta distribution is a probability distribution by itself, it is not associated to the Zipf's law with same exponent. See also Yule–Simon distribution == Moments == The ''n''th raw moment is defined as the expected value of ''X''''n'': : Note that the ratio of the zeta functions is well defined, even for ''n'' ≥ ''s'' − 1 because the series representation of the zeta function can be analytically continued. This does not change the fact that the moments are specified by the series itself, and are therefore undefined for large ''n''. 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「Zeta distribution」の詳細全文を読む スポンサード リンク
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