Chapter 5
The Normal Distribution
IN THIS CHAPTER
Understanding the normal and standard normal distributions
Going from start to finish with regular normal probabilities
Working backward to find percentiles
There are two major types of random variables: discrete and continuous. Discrete random variables basically count things (number of heads on 10 coin flips, number of female Democrats in a sample, and so on). The most well known discrete random variable is the binomial (see Chapter 4). A continuous random variable measures things and takes on values within an interval, or they have so many possible values that they might as well be deemed continuous (for example, time to complete a task, exam scores, and so on).
In this chapter, you work on finding probabilities for the most famous continuous random variable, the normal. You also find percentiles for the normal distribution (where you are given a probability as a percent) and you have to find the value of X that’s associated with it.
Basics of the Normal Distribution
We say that X has a normal distribution if its values fall into a smooth (continuous) curve with a bell-shaped, symmetric pattern, meaning it looks the same ...