Investigation 14: Used car prices (due Wed, Nov 30)

You may work with one other person on this assignment, handing in one report with both names.  Word-processed reports are preferred to hand-written ones. Please copy/paste relevant, well-labeled Minitab output into a Word file as appropriate.

The data in UsedCars.mtw come from a sample of 16 used Honda Civics listed for sale on the web in December 2004. In addition to model of car, other variables recorded are age in years, mileage, and price.

a) Examine scatterplots and correlation coefficients to determine whether age or mileage would be a better predictor of price. Choose one of these explanatory variables, and explain your choice. (Also submit the scatterplots.)

b) Determine the least squares line for predicting price from whichever explanatory variable you selected.

c) Choose a particular value of your explanatory variable, and predict the price of such a car.

d) Conduct a test of whether the sample data provide strong evidence of a linear relationship in the population between price and your explanatory variable. Include all components of the test, and summarize your conclusion.

e) Determine a 95% confidence interval for the population slope coefficient, and interpret what this parameter and interval represent.

f) Choose a particular value of your explanatory variable, and produce a 95% prediction interval for the price of such a car.