Make an Excel graph of the data on U.S. diesel new car sales. (b) Discuss the underlying causes that might explain the trend. (c) Use Excel, MegaStat, or MINITAB to fit three trends (linear, quadratic, and exponential) to the time series. (d) Which trend model do you think is best to make forecasts for the next 3 years? Why? (e) Use each of the three fitted trend equations to make numerical forecasts for 2004, 2005, and 2006. How much difference does the choice of model make? Which forecasts do you trust the most, and why? (f) If you have access to Ward's Automotive Yearbook, check your forecasts. How accurate were they?

U.S. Diesel New Car Sales, 1993-2003
Year Sales
1993 2,800
1994 3,577
1995 3,139
1996 8,469
1997 7,331
1998 10,972
1999 13,573
2000 22,634
2001 15,077
2002 31,430
2003 38,524