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Course: Statistics and probability > Unit 3
Lesson 1: Measuring center in quantitative dataCalculating the mean
Learn how to calculate the mean by walking through some basic examples & trying practice problems.
The mean is used to summarize a data set. It is a measure of the center of a data set. Let's look at an example.
Claire has cookies, Brooke has cookies, Deandra has cookies, and Lucy has cookies. Find the mean number of cookies.
Let's start by drawing a picture to show each person and their cookies:
Imagine that the girls combined all of their cookies
and then each took the same number of cookies.
Each girl would have cookies. So, the mean is cookies.
Key idea: We can think of the mean as the number of cookies each girl would have if they were equally distributed among the four girls.
Calculating the mean
We don't need to draw a picture every time we want to calculate the mean. Instead, we can follow these steps:
Step 1: Add up all of the data points (this is like combining all of the cookies)
Step 2: Divide the total by the number of data points in the data set (this is like each girl taking the same number of cookies)
Let's do this for the data set :
The mean of this data set is .
Calculating the mean walkthrough
Let's find the mean of the data set together.
Great! Now divide the total by the number of data points.
Now it's time to try some practice on your own.
Practice
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