Algebra 1 · Unit 10
Create questions that pair two numerical variables you could actually collect.
Jump to section:
Two variables
A bivariate question names two measurable things and asks how they go together, not just one average.
Be specific
“Does studying help?” is vague. “Among 9th graders, how is minutes of math homework last night related to the quiz score today?” can be graphed.
Both quantitative
This unit’s scatterplots need two numerical variables (hours, scores, dollars, degrees), not yes/no categories.
You must be able to collect it
A good question is one you could actually measure with a survey, a sensor, or a public data set.
Spot a bivariate numerical question.
The first is one variable (height).
The second pairs height with shoe size.
Answer: height and shoe size
Example: How is hours of sports last week related to a fitness-test score?
Answer: hours vs a numerical score
No. One variable: quiz score.
Answer: no
Hours worked last week and dollars earned last week.
Answer: hours and dollars
Minutes of sleep and reaction time. Color is a category.
Answer: sleep and reaction time
How is the high temperature related to cups of lemonade sold that day?
Answer: temperature vs cups sold
Turn a vague idea into a collectible question.
Example: For students in this class, how is minutes of phone use yesterday related to last night’s homework score (out of 10)?
Both numbers, both measurable.
Answer: minutes vs homework score
“Better” is not a number until you define it.
Fix: How is height related to free-throw percentage this season?
Answer: define a number for “better”
How is rainfall (cm) related to tomato mass (g)?
How is hours of sunlight related to number of ripe tomatoes?
Answer: rain vs mass; sun vs count
Example: household size, or minutes spent caring for pets per day.
Answer: need a second numerical variable
The second. Lifetime income is not available this week for classmates.
Answer: practice vs typing speed
How is daily high temperature related to daily rainfall in our city this month?
Answer: high temp vs rainfall
The question must match a scatterplot, not a bar graph of categories.
Line A vs B is a category, not two numbers per person.
Related: How is number of people already in line related to wait time in minutes?
Answer: wait time vs people in line
Happiness needs a scale (1 to 10). Money needs a defined amount (weekly allowance, last month’s spending).
Example: How is last week’s spending (dollars) related to a 1–10 mood rating on Friday?
Answer: define both as numbers
How is day number related to the plant’s height in cm?
Answer: day vs height
(1). Passed/failed is a category, not a second numerical axis.
Answer: sleep vs score
Question: How is minutes of studying yesterday related to today’s test score?
Record, for each student, those two numbers (and maybe a name code).
Answer: minutes and score
Birth month is a category (Jan, Feb, …), not a useful numerical scale for a scatterplot of this type.
Answer: month is a category
Good: How is walking time (min) related to outdoor temperature (°F)?
Good: How is walking time related to number of stoplights that were red?
Poor: Is walking nice?
Answer: two numerical, one vague
Poor: How is exact body weight related to family income?
Replacement: How is self-reported hours of exercise last week related to a timed walk in gym class?
Answer: replace private data
How is hours of practice related to contest score?
Same two variables; the scatterplot is the same cloud. The story of “what we think comes first” is practice → score, not the other way.
Answer: same plot, different story of cause
Need help writing a bivariate question?
Book a Session with Amy