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.
Maine Learning Results learning standard: 8.SP.A.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 Maine
In the Maine Learning Results, 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: Maine Department of Education
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
What percent of the "Grade 8" row are "Walks to school"?
Getting to school Walks to school Rides to school Total Grade 8 13 7 20 Grade 9 25 15 40 Total 38 22 60 - 21.7%
- 34.2%
- 75%
- 65%
65%
Hint: 13 out of 20 = 13 ÷ 20 × 100.
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 15 35 50 Doesn't like reading 23 17 40 Total 38 52 90 - 17
- 35
- 23
- 40
17
Hint: Find the row, then move across to the column.
Question 3
Compare the percent of each row that is "Has a library card". Is there evidence of an association?
Reading survey Has a library card No library card Total Likes reading 43 7 50 Doesn't like reading 11 14 25 Total 54 21 75 - 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: Likes reading: 86%. Doesn't like reading: 44%.
Question 4
How many in all are "Walks to school"?
Getting to school Walks to school Rides to school Total Grade 8 6 34 40 Grade 9 3 17 20 Total ? 51 60 - 6
- 40
- 10
- 9
9
Hint: Add down the column.
Question 5
How many in all are "Has a pet"?
Sports and pets Has a pet No pet Total Plays sports 11 9 20 No sports 17 8 25 Total ? 17 45 - 11
- 29
- 20
- 28
28
Hint: Add down the column.
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 16 4 20 Grade 9 2 23 25 Total 18 27 45 - 25
- 2
- 23
- 4
23
Hint: Find the row, then move across to the column.