Practice: Scatter Plots

Grade 8 Mathematics | Data Analysis

Name:
Date:

Part A: Identify the Association

Directions: For each scatter plot description, identify the type of association: positive, negative, or no association.

1. As the price of a product increases, the number of items sold decreases.

Association:

2. As the number of hours practicing piano increases, the number of mistakes made decreases.

Association:

3. As temperature increases, the number of people at the beach increases.

Association:

4. As a person's height increases, their favorite color shows no pattern.

Association:

Part B: Describe the Association in Context

Directions: Write a sentence describing what the association means in real-world terms.

5. A scatter plot shows a positive association between the number of hours students study and their test scores.

Describe in context:

6. A scatter plot shows a negative association between the age of a car (in years) and its resale value (in dollars).

Describe in context:

Part C: Linear or Non-Linear?

Directions: Determine if each association would likely be linear or non-linear.

7. The height of a ball thrown in the air vs. time

(Hint: Does a ball go up and then come down?)

Linear or Non-linear:

8. Total cost vs. number of items purchased (at a fixed price per item)

(Hint: Is the cost per item constant?)

Linear or Non-linear:

9. Population growth of bacteria that doubles every hour

(Hint: 1, 2, 4, 8, 16...)

Linear or Non-linear:

10. Distance traveled vs. time at a constant speed

Linear or Non-linear:

Part D: Analyze Data

Directions: Use the data to answer the questions.

11-12. The table shows the relationship between hours of TV watched per day and weekly exercise hours.

TV Hours (x)Exercise Hours (y)
110
28
37
45
54
62

11. Type of association:

12. Describe the relationship in context:

13-14. The table shows the relationship between study time and quiz scores.

Study Time (hours)Quiz Score
0.562
170
1.575
282
2.588
394

13. Type of association:

14. Using the pattern, predict the quiz score for 3.5 hours of study:

Part E: Line of Best Fit

Directions: Use the line of best fit information to make predictions.

15. A line of best fit for a scatter plot passes through the points (2, 30) and (8, 60). Use the line to predict the y-value when x = 5.

Hint: Find the rate of change (slope), then use it to find the value at x = 5.

Predicted y-value:

16. A scatter plot shows a positive linear association. A line of best fit has the equation y = 4x + 10. Predict the y-value when x = 7.

Predicted y-value:

Challenge: Think About It!

17. A researcher finds a strong positive association between ice cream sales and drowning incidents. Does eating ice cream cause drowning? Explain what might actually be happening.

18. Two students draw different lines of best fit for the same scatter plot. Student A's line passes through more data points. Student B's line has roughly equal points above and below. Which line is better and why?