Question 13.76

13.76 U.S. air carrier traffic.

How much more or less are Americans taking to the air? Consider a time series of monthly total number of passenger miles (in thousands) on U.S. domestic flights starting with January 2009 and ending with May 2014.40

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  1. Make a time plot of monthly miles. Describe the behavior of the series. Is there a trend? What months are consistently high versus low?
  2. Does the seasonal variation appear to be additive or multiplicative in nature? Justify your answer.
  3. Fit the time series to a trend and monthly indicator variables. Report the estimated model.
  4. Check the residuals from the trend-seasonal model for randomness. What do you conclude?
  5. Forecast the total number of passenger miles to be flown in June 2014.