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Home > CC3 > Chapter 7 > Lesson 7.3.2 > Problem 7-103

7-103.

Marissa’s older sister was discussing purchasing a car with her summer job earnings.  Marissa collected data from her friends at her job. Homework Help ✎

Refer to problem 7-92 for help.

  1. Marissa would like to know the typical age of her friends’ cars.  What kind of graphical display should she use? 

    A box plot shows center and spread of one-variable numerical data nicely.

  1. Marissa wants to convince her dad that newer cars are more fuel-efficient.  What kind of graph(s) should Marissa make to convince her dad? 

    Marissa wants to show her dad an association between age and miles per gallon.

  1. Make a scatterplot of the data.

    Use age as the -axis and mpg as the -axis.

  1. Fully describe the association.

    Weak, negative, linear association.

  1. Draw a line of best fit on the data.  Find the equation of the line of best fit. 

    Remember that when drawing a line of best fit, about half the points should be above the line and about half should be below.

  2. Use the equation to predict what the correct mileage for a -year-old car should be.

    • You should get around mpg.

  1. Interpret the slope and -intercept in this situation.  

    A slope of means that for each additional year old a car is, it is expected to go less miles per gallon.
    What does the -intercept say about a new car?

Age of Car (years)

Fuel Efficiency (mpg)

9

34

2

30

5

30

1

35

4

34

10

28

9

27

3

40

8

29