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We said in class that two events A and B are indep(ndent if μ(An B) 6. μ(A)a(B). Sinilarly, two random variables X and Y are said to be independent if their joint density fx.y(r,y) can be expressed as the product of the marginal densities fx(x)fv(y). Let X and Y be independent (scalar) random variables, and ZX Y be a new random variable defined as the sum of X and Y. Show that the moment generating function mz(t) of Z is a product of moment generating functions of X and of Y, i.e., nız(1) = mx(t)my(t) Recal that if the moment generating function exists, then it uniquely determines the density of the random variable. Now, suppose that X and Y are independent Gaussian random variables with densities N(mx,TX) and N(my,ay); then prove that Z is also a Gaussian random variable and compute its mean and variance

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