8th grade · Math · Unit 17 of 17

Two-Way Tables

Data in rows and columns

What your child practices

Reading two-way tables of survey data, finding relative frequencies (percents) in a row, and deciding whether two things seem to be linked.

California Content Standards learning standard: 8.SP.4 · looking for patterns of association in two-way tables of categorical data

How we explain it

Children can open this short lesson before they practice.

A two-way table sorts data by two questions at once.
Find a row, then read across to the column.
Compare row percents to look for an association.

Example: 20 students play sports; 15 of them have a pet. What percent of them have a pet? 15 ÷ 20 = 0.75. 0.75 = 75%. Answer: 75%

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

Question 1
Compare the percent of each row that is "Felt rested". Is there evidence of an association?
Morning survey
Felt rested Felt tired Total
Ate breakfast 38 2 40
No breakfast 22 3 25
Total 60 5 65
- Yes, the percents are very different
- You can't tell from a two-way table
- Not much, the percents are close
Question 2
How many in the "No sports" row are in the "No pet" column?
Sports and pets
Has a pet No pet Total
Plays sports 7 13 20
No sports 28 22 50
Total 35 35 70
- 22
- 13
- 50
- 28
Question 3
What percent of the "Likes reading" row are "Has a library card"?
Reading survey
Has a library card No library card Total
Likes reading 11 9 20
Doesn't like reading 40 10 50
Total 51 19 70
- 15.7%
- 21.6%
- 65%
- 55%
Question 4
How many in all are "Has a pet"?
Sports and pets
Has a pet No pet Total
Plays sports 2 38 40
No sports 36 14 50
Total ? 52 90
- 40
- 38
- 2
- 39
Question 5
How many in all are "Walks to school"?
Getting to school
Walks to school Rides to school Total
Grade 8 36 4 40
Grade 9 8 17 25
Total ? 21 65
- 36
- 40
- 44
- 45
Question 6
What percent of the "Likes reading" row are "Has a library card"?
Reading survey
Has a library card No library card Total
Likes reading 33 7 40
Doesn't like reading 19 6 25
Total 52 13 65
- 63.5%
- 92.5%
- 82.5%
- 50.8%