Quiz 4

1. Problem 1. The following data represent the weights of ten cars and their gas mileages.

(a) (2 points) What are the explanatory and response variables?
(b) (2 points) What is the correlation coefficient?
(c) (2 points) What type of relationship exists between the weight of a car and its gas mileage?
(d) (2 points) Find the equation of the least squares regression line.
(e) (2 points) Find and interpret the slope.
(f) (2 points) A Cadillac CTS weighs 3649 pounds and gets 20 miles per gallon. Is the miles per gallon of a Cadillac CTS above average or below average for cars of this weight?
(g) (2 points) Would it be reasonable to use the least-squares regression line to predict the miles per gallon of a Toyota Prius, which is a hybrid electric car? Why?

2. Problem 2. The linear correlation between violent crime rate and percentage of the population that has a cell phone is r = −0.918 for years since 1995.

(a) (1 point) What does this correlation imply?
(b) (1 point) Can we conclude that increasing the percentage of the population that has a cell phone will decrease the
violent crime rate?