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The maximum discount value of the Entertainment® card for the “Fine Dining” section, Edition 10, for various pages is given below.

Page number Maximum value ($)
4 16
14 19
25 15
32 17
43 19
57 15
72 16
85 15
90 17

  • Decide which variable should be the independent variable and which should be the dependent variable.
  • Draw a scatter plot of the ordered pairs.
  • Calculate the least squares line. Put the equation in the form of: y ^ = a + bx size 12{y=a+ ital "bx"} {}
  • Find the correlation coefficient. Is it significant?
  • Find the estimated maximum values for the restaurants on page 10 and on page 70.
  • Use the two points in (e) to plot the least squares line on your graph from (b).
  • Does it appear that the restaurants giving the maximum value are placed in the beginning of the “Fine Dining” section? How did you arrive at your answer?
  • Suppose that there were 200 pages of restaurants. What do you estimate to be the maximum value for a restaurant listed on page 200?
  • Is the least squares line valid for page 200? Why or why not?
  • What is the slope of the least squares (best-fit) line? Interpret the slope.

The next two questions refer to the following data: The cost of a leading liquid laundry detergent in different sizes is given below.

Size (ounces) Cost ($) Cost per ounce
16 3.99
32 4.99
64 5.99
200 10.99
  • Using “size” as the independent variable and “cost” as the dependent variable, make a scatter plot.
  • Does it appear from inspection that there is a relationship between the variables? Why or why not?
  • Calculate the least squares line. Put the equation in the form of: y ^ = a + bx size 12{y=a+ ital "bx"} {}
  • Find the correlation coefficient. Is it significant?
  • If the laundry detergent were sold in a 40 ounce size, find the estimated cost.
  • If the laundry detergent were sold in a 90 ounce size, find the estimated cost.
  • Use the two points in (e) and (f) to plot the least squares line on your graph from (a).
  • Does it appear that a line is the best way to fit the data? Why or why not?
  • Are there any outliers in the above data?
  • Is the least squares line valid for predicting what a 300 ounce size of the laundry detergent would cost? Why or why not?
  • What is the slope of the least squares (best-fit) line? Interpret the slope.
  • Yes
  • y ^ = 3 . 5984 + 0 . 0371 x size 12{y=3 "." "5984"+0 "." "0371"x} {}
  • 0.9986; Yes
  • $5.08
  • $6.93
  • No
  • Not valid
  • slope = 0.0371. As the number of ounces increases by one, the cost of liquid detergent tends to increase by $0.0371 or is predicted to increase by $0.0371 (about 4 cents).
  • Complete the above table for the cost per ounce of the different sizes.
  • Using “Size” as the independent variable and “Cost per ounce” as the dependent variable, make a scatter plot of the data.
  • Does it appear from inspection that there is a relationship between the variables? Why or why not?
  • Calculate the least squares line. Put the equation in the form of: y ^ = a + bx size 12{y=a+ ital "bx"} {}
  • Find the correlation coefficient. Is it significant?
  • If the laundry detergent were sold in a 40 ounce size, find the estimated cost per ounce.
  • If the laundry detergent were sold in a 90 ounce size, find the estimated cost per ounce.
  • Use the two points in (f) and (g) to plot the least squares line on your graph from (b).
  • Does it appear that a line is the best way to fit the data? Why or why not?
  • Are there any outliers in the above data?
  • Is the least squares line valid for predicting what a 300 ounce size of the laundry detergent would cost per ounce? Why or why not?
  • What is the slope of the least squares (best-fit) line? Interpret the slope.

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Source:  OpenStax, Collaborative statistics (custom online version modified by t. short). OpenStax CNX. Jul 15, 2013 Download for free at http://cnx.org/content/col11476/1.5
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