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?

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Sales Year Sales Year 1980 105 1989 75 1981 126 1990 1982 101 1991 72 1992 1983 107 78 103 90 1984 1993 79 1985 1994 100 1986 1995 98 1987 85 1996 93 1988 104 90 1997