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.
Alabama Course of Study content standard: 8.21 · reading two-way tables of categorical data with relative frequencies
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 Alabama
In the Alabama Course of Study, 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.
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
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 13 12 25 Grade 9 35 15 50 Total 48 27 75 - 15
- 35
- 12
- 50
15
Hint: Find the row, then move across to the column.
Question 2
How many in all are "Walks to school"?
Getting to school Walks to school Rides to school Total Grade 8 10 15 25 Grade 9 2 18 20 Total ? 33 45 - 13
- 10
- 12
- 25
12
Hint: Add down the column.
Question 3
What percent of the "Plays sports" row are "Has a pet"?
Sports and pets Has a pet No pet Total Plays sports 4 16 20 No sports 20 20 40 Total 24 36 60 - 16.7%
- 20%
- 30%
- 6.7%
20%
Hint: 4 out of 20 = 4 ÷ 20 × 100.
Question 4
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 43 7 50 No sports 7 43 50 Total 50 50 100 - Not much, the percents are close
- Yes, the percents are very different
- You can't tell from a two-way table
Yes, the percents are very different
Hint: Plays sports: 86%. No sports: 14%.
Question 5
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 5 45 50 Grade 9 38 12 50 Total 43 57 100 - 38
- 45
- 50
- 12
12
Hint: Find the row, then move across to the column.
Question 6
How many in all are "Felt rested"?
Morning survey Felt rested Felt tired Total Ate breakfast 23 2 25 No breakfast 5 15 20 Total ? 17 45 - 25
- 28
- 23
- 29
28
Hint: Add down the column.