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Normal characterization by zero correlations
Published online by Cambridge University Press: 09 April 2009
Abstract
Suppose Xi, i = 1,…,n are indepedent and identically distributed with E/X1/r < ∞, r = 1,2,…. If Cov (( − μ)r, S2) = 0 for r = 1, 2,…, where μ = EX1, S2 =
, and
, then we show X1 ~ N (μ, σ2), where σ2 = Var(X1). This covariance zero condition charaterizes the normal distribution. It is a moment analogue, by an elementary approach, of the classical characterization of the normal distribution by independence of
and S2 using semi invariants. More generally, if Cov
= 0 for r = 1,…, k, then E((X1 − μ)/σ)r+2 = EZr+2 for r = 1,… k, where Z ~ N(0, 1). Conversely Corr
may be arbitrarily close to unity in absolute value, but for unimodal X1, Corr2(
< 15/16, and this bound is the best possible.
MSC classification
- Type
- Research Article
- Information
- Journal of the Australian Mathematical Society , Volume 81 , Issue 3 , December 2006 , pp. 351 - 361
- Copyright
- Copyright © Australian Mathematical Society 2006
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