#### Mean and Standard Deviation of Binomial Random Variables (Jump to: Lecture | Video )

Let's use the data from the last lecture: In a recent survey, it was found that 85% of households in the United States
have High-Speed Internet. If you take a sample of 18 households, what is the probability that exactly 15 will
have High-Speed Internet?

Here are the equations for mean and standard deviation of a binomial random variables:

We can now easily plug in the number of trials and the probability of success to come up with our answers:

The mean is 15.3, and the standard deviation is 1.515.