First decide on a car model you like. Then go to an internet auction where cars are offered (I guess ebay also has now such a section) and select at least 30 such cars randomly (don't just take the first 30 hits, you have to describe in your paper how you selected your sample and why it is a simple random sample). Make a table listing the price asked, the milage, and the year.
Next find out whether there is some correlation between these three variables. If there is one, find the correlation coefficient and the regression line.
Also compute the standard error of estimate for this regression line.
Do the same for another car model. Compare the regression lines, the correlation coefficients, and the standard error of estimate for both models.
creating data, paired data, regression and correlation
Erich Prisner, May 2006