Problem
Refer to the case study Impact of September 11 on Air Travel in the United States, discussed on pages 23&42. The data is in file Sept11Travel.csv. In order to assess the impact of September 11, BTS took the following approach: Using data before September 11, it forecasted future data (under the assumption of no terrorist attack). Then, BTS compared the forecasted series with the actual data to assess the impact of the event.
i. Is the goal of this study descriptive or predictive?
ii. What is the forecast horizon to consider in this task? Are next-month forecasts sufficient?
iii. What level of automation does this forecasting task require? Consider the four questions related to automation.
iv. What is the meaning of t = 1, 2, 3 in the Air series? Which time period does t = 1 refer to?
v. What are the values for y1, y2, and y3 in the Air series?
vi. Plot the Air series for both entire time series and pre-event time series.
vii. What time series components appear from the plot?
viii. What type of trend appears? Discuss.