16/10/07 16:36:42.67 ++KBxzq2.net
>>22 関連
URLﾘﾝｸ(ja.wikipedia.org) 冪乗則
URLﾘﾝｸ(en.wikipedia.org)
Power law
(抜粋)
Lack of well-defined average value
A power-law x^(-a) has a well-defined mean over x ∈ [ 1 , ∞ ] only if a > 2 , and it has a finite variance only if a > 3 ; most identified power laws in nature have exponents such that the mean is well-defined but the variance is not, implying they are capable of black swan behavior.[8]