Copyright © Cengage Learning. All rights reserved. 6 Normal Probability Distributions

Copyright © Cengage Learning. All rights reserved. 6.1 Normal Probability Distributions

3 Intelligence Scores

4 The normal probability distribution is considered the single most important probability distribution. An unlimited number of continuous random variables have either a normal or an approximately normal distribution. We are all familiar with IQ (intelligence quotient) scores and/or SAT (Scholastic Aptitude Test) scores. IQ scores have a mean of 100 and a standard deviation of 16. SAT scores have a mean of 500 with a standard deviation of 100. But did you know that these continuous random variables also follow a normal distribution?

5 Intelligence Scores

6 We learned how to use a probability function to calculate probabilities associated with discrete random variables. The normal probability distribution has a continuous random variable and uses two functions: one function to determine the ordinates (y values) of the graph displaying the distribution, and a second function to determine probabilities.

7 Intelligence Scores Probability distribution, continuous variable A formula or a list that provides the probability for a continuous random variable having a value falling within a specified interval. The probability distribution is a theoretical distribution; it is used to represent populations.