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a) Prove that if Y is a random variable with all of its cumulants of order...

a) Prove that if Y is a random variable with all of its cumulants of order greater than two equal to zero, i.e., 0 = K_3 = K_4 = ......... then Y has a normal distribution.

b) Suppose that Z has cumulant generating function k_Z(t) with E(Z) = 0 and Var(Z) = 1. Let Y = σZ + μ. Find the cumulant generating function of Y , k_Y (t) in terms of k_Z(.). Use this to prove that all cumulants except K_1 are location invariant, i.e. do not depend on μ.

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