The probability density function (PDF) of the sum of two independent continuous random variables X and Y is given by the convolution of the PDFs: fx * fy = ∫ fx(x) * fy(y-x) dx. Show that the sum of two independent standard normal variables results in a normal variable. Find the PDF of such sum. Give four solutions in two ways: 1) using the convolution function above; 2) by using moment generating functions.
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The PDF of the sum $Z = X + Y$ is given by the convolution of $f_X(x)$ and $f_Y(y)$: $$f_Z(z) = \int_{-\infty}^{\infty} f_X(x) f_Y(z - x) dx$$ Since $X$ and $Y$ are standard normal random variables, their PDFs are given by: $$f_X(x) = \frac{1}{\sqrt{2\pi}} Show more…
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