Practice question #5 The following data is from 93 models of cars sold in 1993. The length of the wheelbase in inches is graphed against the mileage (MPG highway). a. Does this data seem to have a positive or negative correlation coefficient? Explain. b. ?2 = .38. Fill in the blanks. This means that ___________ % of the ________________________ in the mileage is explained by the _____________________________ relationship between wheelbase and MPG. c. Based on the above two questions, what must the value of r be to two decimal places? d. Based on above answer, what can you say about the strength of the correlation? Explain based on the rules for strength in our textbook. e. If the correlation coefficient for these two variables were instead r = 0, what would that have implied about the relationship (be specific)? f. The least squares regression line is ?� = −0.48? + 79.10. If a car has a wheelbase of 105 inches, what would you expect its highway MPG to be? Show work. g. If we were to build a car with a wheelbase of 130 inches, it would not be appropriate to predict the mileage. What concept would this be an example of and why is it a problem? (You do not have to calculate anything here).
Practice question #5 The following data is from 93 models of cars sold in 1993. The length of the wheelbase in inches is graphed against the mileage (MPG highway).
a. Does this data seem to have a positive or negative
b. ?2 = .38. Fill in the blanks. This means that ___________ % of the ________________________
in the mileage is explained by the _____________________________ relationship between wheelbase
and MPG.
c. Based on the above two questions, what must the value of r be to two decimal places?
d. Based on above answer, what can you say about the strength of the correlation? Explain based on the
rules for strength in our textbook.
e. If the correlation coefficient for these two variables were instead r = 0, what would that have implied
about the relationship (be specific)?
f. The least squares regression line is ?� = −0.48? + 79.10. If a car has a wheelbase of 105 inches, what
would you expect its highway MPG to be? Show work.
g. If we were to build a car with a wheelbase of 130 inches, it would not be appropriate to predict the
mileage. What concept would this be an example of and why is it a problem? (You do not have to
calculate anything here).
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