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.
Alaska 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%
Two-Way Tables in Alaska
In the Alaska content standards, this is unit 17 of 17 in 8th grade Math, after Slope & Rate of Change.
Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.
Source: Alaska Department of Education and Early Development
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 "Has a pet". Is there evidence of an association?
Sports and pets Has a pet No pet Total Plays sports 14 11 25 No sports 9 31 40 Total 23 42 65 - You can't tell from a two-way table
- Not much, the percents are close
- Yes, the percents are very different
Yes, the percents are very different
Hint: Plays sports: 56%. No sports: 23%.
Question 2
How many in the "Doesn't like reading" row are in the "No library card" column?
Reading survey Has a library card No library card Total Likes reading 6 14 20 Doesn't like reading 15 25 40 Total 21 39 60 - 40
- 15
- 14
- 25
25
Hint: Find the row, then move across to the column.
Question 3
What percent of the "Ate breakfast" row are "Felt rested"?
Morning survey Felt rested Felt tired Total Ate breakfast 24 16 40 No breakfast 32 18 50 Total 56 34 90 - 42.9%
- 60%
- 70%
- 26.7%
60%
Hint: 24 out of 40 = 24 ÷ 40 × 100.
Question 4
How many in all are "Has a pet"?
Sports and pets Has a pet No pet Total Plays sports 14 11 25 No sports 16 24 40 Total ? 35 65 - 14
- 25
- 31
- 30
30
Hint: Add down the column.
Question 5
What percent of the "Plays sports" row are "Has a pet"?
Sports and pets Has a pet No pet Total Plays sports 2 38 40 No sports 28 12 40 Total 30 50 80 - 5%
- 15%
- 2.5%
- 6.7%
5%
Hint: 2 out of 40 = 2 ÷ 40 × 100.
Question 6
How many in the "Grade 9" row are in the "Rides to school" column?
Getting to school Walks to school Rides to school Total Grade 8 20 20 40 Grade 9 5 15 20 Total 25 35 60 - 5
- 17
- 20
- 15
15
Hint: Find the row, then move across to the column.