The price of a car depends on its age as well as on its mileage. Here is a regression in which the age of the cars (in years) is included in the regression model from Exercise 34:

a) What is the interpretation of the coefficient of miles(000) in this regression? Why is it so different from the interpretation in the model of Exercise 34?
Here is a a partial regression plot for the coefficient of miles(000)

b) What is the slope of this plot? How do you know?
c) What effect does the point in the upper left have on the coefficient and P-value of miles(000)?

Data From Exercise 34

On January 22, 2017, www.autotrader.com listed 55 used Honda Civics for sale by owner. Here’s a scatterplot of the asking price vs. the number of miles on the odometer (in thousands):

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Response variable is: Price R squared = 86.1% s = 1957 with 55 - 3 = 52 degrees of freedom Coefficient SE(Coeff) t-ratio Variable Intercept 17751.4 430.5 41.2 miles(000) age -53.5638 -389.373 7.809 77.47 -6.86 -5.03 P-value <0.0001 <0.0001 <0.0001