1. The file ToyotaCorolla.xls contains data on used cars (ToyotaCorollas) on sale during late summer of 2004 in The Netherlands. It has 1,436 records containing details on 38 attributes, including Price, Age, Kilometers, HP, and other specifications. The goal will be to estimate the price of a used Toyota Corolla based on its specifications. Let Y represent the price, X1 the age ("age_08_04), X2 Guarantee period, and X3 the automatic (yes=1, no=0).

(1) If you have to use a simple linear regression model to estimate the selling price of a car, which X variable do you want to use? Why?

(2) Develop a multiple linear regression model by using X1 and X2. Report coefficients of X1 and X2, and interpret them. Does X2 help to explain the selling price of the cars?

(3) Develop a multiple linear regression model by using X1 and X3, and report their coefficients and interpret them. Does X3 help to explain the selling price of the cars? How much does an automatic option add to the value of a car?

You can find the raw file at here

https://github.com/SeongCheol-Kim/2016_summer/blob/master/ToyotaCorolla.xls