In probability theory, the method of moments is a way of proving convergence in distribution by proving convergence of a sequence of moment sequences. Suppose X is a random variable and that all of the moments
E ( X k ) {\displaystyle \operatorname {E} (X^{k})\,}
exist. Further suppose the probability distribution of X is completely determined by its moments, i.e., there is no other probability distribution with the same sequence of moments (cf. the problem of moments). If
lim n → ∞ E ( X n k ) = E ( X k ) {\displaystyle \lim _{n\to \infty }\operatorname {E} (X_{n}^{k})=\operatorname {E} (X^{k})\,}
for all values of k, then the sequence {Xn} converges to X in distribution. The method of moments was first introduced in 1891 by Pafnuty Chebyshev for proving the central limit theorem; although his proof is considered incomplete. Chebyshev cited earlier contributions by Irénée-Jules Bienaymé. More recently, the method has been applied by Eugene Wigner to prove Wigner's semicircle law, and has since found numerous applications in the theory of random matrices.
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