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Covariance of X with the square of a correlated normal

Question

Suppose (X,Y)(X,Y) is bivariate normal, each coordinate standard normal, with correlation ρ\rho. What is Cov⁡(X,Y2)\operatorname{Cov}(X,Y^2)?

Short answer

00. Since E[X]=0\mathbb{E}[X]=0, the covariance equals E[XY2]\mathbb{E}[XY^2]. The pair (−X,−Y)(-X,-Y) has the same joint law as (X,Y)(X,Y), and XY2XY^2 changes sign under this flip, so its expectation is zero for every ρ\rho.

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