Once we know what a random variable is, we will look at important properties of a random variable. Most important are its expected value and its variance. We will look the definitions as well as the intuition behind these properties. Next, we can create a new random variable from an old one. If the new one is a linear function of the old one, then figuring out its expected value and variance is particularly simple. We end this section with the normal random variables which may have any expected value and any positive variance.