The annual number of international visitors to the United States from 2000 through 2007 is shown here.
Year Visitors (millions)
2000........ 50.9
2001........ 44.9
2002........ 41.9
2003........ 41.2
2004........ 46.1
2005........ 49.4
2006........ 51.0
2007........ 56.0
a. Fit a linear trend equation to the time series. Using this equation, determine the trend estimate for 2015.
b. Fit a quadratic equation to the time series, then use the equation to determine the trend estimate for 2015.
c. Which of the preceding equations is the better fit to the time series if the MAD criterion is used? If the MSE criterion is used?