Let Z and W be independent standard normal random

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QUESTION:

Let Z and W be independent standard normal random variables. Let X and Y be defined by

X = σ1Z + μ1

Y = σ2[ρZ √1 - ρ2W] μ2

Where, σ1,σ2 > 0,–∞ < μ1, μ2 < ∞ and –1 < ρ < 1. Show that the joint probability density function of X and Y is bivariate normal and σ1 = σX2 = σY1 = μX2 = μY and ρ = ρ(X,Y).

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QUESTION:

Let Z and W be independent standard normal random variables. Let X and Y be defined by

X = σ1Z + μ1

Y = σ2[ρZ √1 - ρ2W] μ2

Where, σ1,σ2 > 0,–∞ < μ1, μ2 < ∞ and –1 < ρ < 1. Show that the joint probability density function of X and Y is bivariate normal and σ1 = σX2 = σY1 = μX2 = μY and ρ = ρ(X,Y).

ANSWER:

Step 1 of 4

Let and be independent standard normal random variables. Suppose and be defined by

Here, and .

To prove that the joint probability density function of and is bivariate normal.

Since , therefore, implying has normal distribution.

Now, . Since and be independent standard normal random variables and are constants, therefore, by considering ,

It is a linear transformation of . Therefore, for all and ,  has normal distribution.

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