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.
Washington State Learning Standards learning standard: M.8.DA.SP.4 · reading two-way tables of categorical data and using relative frequencies to look for an association
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
Not much, the percents are close
Hint: Ate breakfast: 95%. No breakfast: 88%.
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
22
Hint: Find the row, then move across to the column.
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%
55%
Hint: 11 out of 20 = 11 ÷ 20 × 100.
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
38
Hint: Add down the column.
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
44
Hint: Add down the column.
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%
82.5%
Hint: 33 out of 40 = 33 ÷ 40 × 100.