Chapter 7

# The Binomial Distribution

IN THIS CHAPTER

Understanding the binomial distribution

Finding probabilities using the formula and table

Determining the mean and variance

Estimating probabilities in large cases with the normal approximation

In this chapter, you find out how the binomial distribution helps you work with data that has only two outcomes: yes or no — for example, whether someone owns a cellphone or whether a certain drug worked for a disease. You see how to distinguish the binomial from other types of distributions, and you find probabilities for a binomial in small, medium, and large sample cases.

## Characterizing the Binomial Distribution

The term binomial means “two names,” which comes from the fact that each individual observation in this situation has only one of two possible outcomes: yes or no. The binomial random variable counts the number of yeses that occur among all the observations. For example, if you flip a coin ten times, each flip results in either a head (which you may call a yes) or a tail (which you may call a no). The binomial random variable ...

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