网页Every cumulant is just r times the corresponding cumulant of the corresponding geometric distribution. The derivative of the cumulant generating function is K′(t) = r·((1 − p) −1 ·e −t −1) −1. The first cumulants are κ 1 = K′(0) = r·(p −1 −1), and κ 2 = K′′(0) = κ 1 ·p −1.
网页The term cumulant was coined by Fisher (1929) on account of their behaviour under addition of random variables. Let S = X + Y be the sum of two independent random variables. The moment generating function of the sum is the product MS(ξ) = MX(ξ)MY (ξ), and the cumulant generating function is the sum KS(ξ) = KX(ξ)+KY (ξ).
网页the term cumulant was suggested by Hotelling in a letter to Fisher, who approved of the coinage. Let S= X+ Y be the sum of two independent random variables. The moment generating function of the sum is the product M S(˘) = E(e˘(X+Y)) = E(e˘Xe˘Y) = M X(˘)M Y(˘); and the cumulant generating function of the sum is the sum of the cumulant
网页For d>1, the nth cumulant is a tensor of rank nwith dn components, related to the moment tensors, m l, for 1 ≤ l≤ n. For example, the second cumulant matrix is given by c(ij) 2 = m (ij) 2 −m (i) 1 m (j) 1. 3 Additivity of Cumulants A crucial feature of random walks with independently identically distributed (IID) steps is that cumulants ...
网页Moments of the random variable can then be generated as terms of the coecients of the Taylor expansion of G( ) around the origin. Another useful quantity is the cumulant generating function which is the logarithm of the moment characteristic function.
网页2024年8月22日 · Let phi (t) be the characteristic function, defined as the Fourier transform of the probability density function P (x) using Fourier transform parameters a=b=1, phi (t) = F_x [P (x)] (t) (1) = int_ (-infty)^inftye^ (itx)P (x)dx. (2) The cumulants kappa_n are then defined by lnphi (t)=sum_ (n=1)^inftykappa_n ( (it)^n)/ (n!)