1. Means and Variances of Random Variables

2. Recall that for a given set of numbers x1, x2,
Recall that for a given set of numbers x1, x2, , xn, its mean ¯x and variance s2 are defined as

3. A random variable X is usually described by its probability distribution
Probabilities need to be took into account in calculating the mean and variance of a random variable.

4. Example

5. Mean and the Standard Deviation
Suppose that X is a discrete random variable whose probability distribution is
The mean (also called the expected value) μX of X is defined by .

7. Find the mean, variance, and standard deviation.

9. Rules for Means and Standard Deviations

10. Example