The following data show U.S. retail sales of canoes from 1980 through 1997, with data in thousands of boats.
a. Construct a graph of the time series. Does the overall trend appear to be upward or downward?
b. Construct a three-year centered moving average for this series.
c. Using the constant α = 0.3, fit an exponentially smoothed curve to the original time series.
d. Repeat part (c) using α = 0.7. How has the new value for the constant affected the smoothness of the fitted curve?