1. Scatter Plots
By Irma Crespo 2010

2. Definition
A scatter plot is a graph that shows the relationship, if any relationship exists, between two sets of data.
Scatter plots often show a pattern, trend, or relationship.
They are useful for making predictions or for finding out the connection between two sets of data.

3. Types of Relationships
Positive Relationship
Negative Relationship
No Relationship y x y x y x
As x increases,
y increases
As x increases,
y decreases
No obvious pattern

4. Identify the Relationship Look at the Graph
300
200
100 12 4 8
Distance Traveled (mi)
Fuel Remaining (gal) y x
Negative
As the distance traveled in miles increases, the fuel in gallons decreases.
As x increases, y decreases.

5. Identify the Relationship Look at the Graph2 10 8 6 4 20 30 40 50
Experience (weeks)
Keyboard Speed (wpm) y x
Positive
As the number of weeks of experience increases, the keyboarding speed increases.
As x increases, y increases.

6. Identify the Relationship Look at the Graph6 10 9 8 7 12
10.8
11.2
11.6
Shoe Size
Running (s) y x
12.4
No relationship
The time in running does not depend on shoe size.
No obvious pattern.

7. Identify the Relationship Look at the Graph10 50 40 30 20 90 60 70 80
Study Time (minutes)
Test Score y x
100
Positive
As the number of study time increases, the test score increases.
As x increases, y increases.

8. What’s the relationship? Use Common Sense
your age
your grade level
and
Positive
Relationship

9. What’s the relationship? Use Common Sense
number of written words
amount of ink
and
Negative Relationship

10. What’s the relationship? Use Common Sense
time spent studying
grade on test
Grade
and
Positive Relationship

11. What’s the relationship? Use Common Sense
your height
the temperature outside
and
No Relationship

12. What’s the relationship? Use Common Sense
number of times a pencil is sharpened
the length of
the pencil
and
Negative Relationship

13. Line of (Best) Fit Measuring the Relationship
Getting the slope:
Get two points.
Compute for rise divided by run.
The table below shows the average and maximum longevity of various animals in captivity.
y = 3/2 x + 18
Longevity (years)
Average
Maximum 12 47 25 50 15 40 8 20 35 70 77 41 61 54 30 35 40 45 70 20 10 5 15 25 50 60 80
Average
Maximum
(35, 70)
(15, 40)

14. Exit Slip On a separate sheet of paper, answer the following:
Example of a positive relationship.
Example of a negative relationship.
Example of no relationship.

15. Practice Worksheet Complete the practice worksheet.
Work with a partner or on your own.
Submit completed worksheet for grading.
Solutions are discussed the next day.

16. Main Resources
Day, et.al. (2009). Math Connects: Concepts, Skills, and Problem Solving. Section 9.2. Columbus:McGraw-Hill.
PowerPoint created by Irma Crespo.
University of Michigan-Dearborn, School of Education. Winter 2010.