# Lesson 1

Two-way Tables

### Lesson Narrative

The mathematical purpose of this lesson is to create and interpret two-way tables. Two-way tables are used to organize data on two categorical variables. Students encounter the term categorical variable, which is a variable that represents data which can be divided into groups or categories. In statistics, a variable is a characteristic that can take on different values. In eighth grade, students had the opportunity to use two-way tables. The first few tasks incorporate some embedded review. In later lessons, students create and interpret two-way tables showing relative frequencies. When students answer questions about some data, they are making use of the structure of the tables (MP7) to organize and understand the information from descriptions of data. In the Information Gap activity, students must make sense of problems and persevere in solving them (MP1) and attend to the precision of their language (MP6) to ask appropriate questions of their peers.

### Learning Goals

Teacher Facing

• Calculate the total number of individuals in a group given a two-way table.
• Create two-way tables based on information given in everyday language.
• Interpret values (orally and in writing) in two-way tables.

### Student Facing

• Let’s look at categorical data.

### Required Preparation

Print and cut the blackline master for the Info Gap lesson. Make one copy of the blackline master for every 2 students.

### Student Facing

• I can calculate missing values in a two-way table.
• I can create a two-way table for categorical data given information in everyday language.
• I can describe what the values in a two-way table mean in everyday language.

### Glossary Entries

• categorical variable

A variable that takes on values which can be divided into groups or categories. For example, color is a categorical variable which can take on the values, red, blue, green, etc.

• two-way table

A way of organizing data from two categorical variables in order to investigate the association between them.

has a cell phone does not have a cell phone
10–12 years old 25 35
13–15 years old 38 12
16–18 years old 52 8
• variable (statistics)

A characteristic of individuals in a population that can take on different values

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