About This Book

This book was made in 2013 by the University of Utah and the Utah State Office of Education. People can share and reuse this book for free, as long as they follow some simple rules.

What's Inside This Chapter

Chapter 6: Looking at Two Things Together (2 weeks)

This chapter is about a math topic called statistics. Statistics means looking at information (called data) to find patterns.

In this chapter, we look at bivariate data. That's a big word that just means "data about two things at once." For example, you might look at both a person's height AND their age at the same time, to see if they are connected.

Here is what you will learn, in order:

• How to read and make a scatter plot (a graph with dots that shows two things compared)
• How to find patterns in the dots, like whether they go up together, go down together, or don't seem connected at all
• How to draw a "best fit" line through the dots to show the pattern
• How to use that line to guess new numbers
• How to make a two-way table, which is a chart that compares two types of information, like "Do you have a curfew?" and "Do you have chores?"

What You Should Already Know

Before this chapter, you learned about looking at just ONE thing at a time in a set of data, like just people's ages, or just people's heights. Now you will learn to compare TWO things at the same time.

What You Will Learn Next

Later, you will learn more ways to draw lines through dot graphs using computers. You will also learn a number that tells you how strong a pattern is, and other tools to check if your line fits well.

Examples From the Chapter

Tomato Example:
Emina loves eating tomatoes from her garden. She asked her friend Renzo, "Don't you love tomatoes?" Renzo said, "No way! I don't even like looking at them at the store." Emina thought about it. She grows her own tomatoes, so she doesn't buy them at the store either. She wondered: "Do people who like tomatoes also grow gardens at home?"

To answer this, students collect information from people and put it into a two-way table. Then they study the table to see if liking tomatoes is connected to having a garden.

Car Repair Example:
There is a chart showing how many oil changes a car gets, and how much the car's repairs cost. Students plot this information on a graph. Then they write a math rule (called a prediction function) to guess repair costs based on the number of oil changes. They use their rule to guess the cost for 8 oil changes, then check their answer with a partner.

Basketball Example:
Using a scatter plot, students check if there's a connection between how many shots a player tries and how many shots they make. They look for patterns and describe what they notice.

Tongue Twister Example:
Students take turns saying a tongue twister, like "Peter Piper picked a peck of pickled peppers." First, only one student says it. Then two students say it together. Each time, one more student joins in, and the class times how long it takes. This helps students collect their own data to study.