Scatter Plots and Trend Lines
A free Algebra I lesson from the “Statistics and Data Analysis” unit, with a worked example and practice problems including step-by-step solutions.
A scatter plot graphs paired data on two axes. The pattern shows the type and strength of the relationship: rising (positive), falling (negative), random (none); straight-line (linear) or curved (nonlinear); tightly clustered (strong) or spread out (weak). Even strong correlation does not prove that one variable causes the other. In Statistics and Data Analysis, students need more than a memorized rule: they need to recognize the structure, select a method, carry out the algebra cleanly, and interpret the answer in a graph, table, equation, or real context. The expanded practice now mixes skill fluency, transfer questions, and cumulative review so the lesson builds durable Algebra I readiness.
What you'll learn
- Read a scatter plot for positive, negative, or no association
- Distinguish linear and nonlinear trends
- Recognize that correlation does not prove causation
Worked example
Problem. A scatter plot of (hours studied, test score) rises to the right. What type of association is this?
- Both variables increase together.
- That is a positive association.
- Connect the result back to Scatter Plots and Trend Lines so the method and meaning are both clear.
- Check the result against the original representation before writing the final answer.
Answer: Positive
Lesson preview: this page shows 5 practice items. The interactive activity contains 28 practice items and 15 quiz items (multiple choice and typed response). Counts include repeated prompts and variants.
Practice problems
1. Hours practiced vs. free throws made (rising). Association?
Choices: Positive · Negative · None
Show solution
- Both increase together.
Answer: Positive
2. Drink size vs. soda calories (rising). Association?
Choices: Positive · Negative · None
Show solution
- Bigger drinks have more calories.
Answer: Positive
3. Ice-cream sales and drowning incidents both rise in summer. Does ice cream cause drowning?
Choices: Yes (causation) · No (just correlation)
Show solution
- A third variable (hot weather) drives both.
- Correlation does not imply causation.
Answer: No (just correlation)
4. Hours of TV vs. grades (falling). Association?
Choices: Positive · Negative · None
Show solution
- More TV, lower grades — opposite directions.
Answer: Negative
5. Random scatter with no pattern. Association?
Choices: Positive · Negative · None
Show solution
- No discernible trend.
Answer: None
Practice this interactively with instant feedback and an AI tutor.
Practice Scatter Plots and Trend Lines Take the free placement check