1. Given the time series in Exercise 18.65, and using exponential smoothing with a 5 0.5, what would have been the forecast for 2009?
2. Construct three-period and four-period centered moving averages for the quarterly J. C. Penney sales in Exercise 18.67. Are there any other retailing companies for whom a four-period moving average might have such a great effect on smoothing quarterly sales data? If so, give a real or hypothetical example of such a company.
3. The following data describe quarterly residential natural gas sales from 2005 through 2008. Determine the quarterly seasonal indexes, then use these indexes to deseasonalize the original data. Source: U.S. Energy Information Administration, eia.doe.gov, August 22, 2009.
Residential Gas Sales (Trillions of Cubic Feet)
|
|
I
|
II
|
III
|
IV
|
|
2005
|
2329
|
784
|
353
|
1360
|
|
2006
|
2042
|
700
|
349
|
1277
|
|
2007
|
2317
|
761
|
346
|
1294
|
|
2008
|
2351
|
762
|
345
|
1408
|