Refer to the data given in Problem 16.15 on page 682 that represent the amount of oil (in billions of barrels) held in the U.S. strategic reserve from 1981 through 2009 (stored in Strategic).
a. Fit a third-order autoregressive model to the amount of oil and test for the significance of the third-order autoregressive parameter. (Use α = 0.05.)
b. If necessary, fit a second-order autoregressive model to the amount of oil and test for the significance of the second-order autoregressive parameter. (Use α = 0.05.)
c. If necessary, fit a first-order autoregressive model to the amount of oil and test for the significance of the first-order autoregressive parameter. (Use α = 0.05.)
d. If appropriate, forecast the barrels held in 2010.
e. The actual physical capacity of the strategic oil reserve is 727 billion barrels of oil. If you knew that before making a forecast in (d), how would that change your forecast?