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Plot Data, Discuss pattern, Fitted Trend, Forecast

Instruction:
? a) Plot the data
? b) Discuss the pattern and possible causes
? c) Would a fitted trend be helpful?
? d) Does 1992-2003 graph suggest fitted trend can predict 2004?
? e) Fit a trend model to 1992-2004 data
? f) Make a forecast for 2004
? g) Why is it best to ignore earlier data?

The table below shows the number of aircraft delivered by U.S. manufacturers to the general aviation market for a 38-year period. "General aviation" is defined as all aviation activities aside from military and scheduled passenger or freight airline flights. General aviation includes business jets, flight training aircraft, crop dusters, pleasure flight, experimental aircraft, charter airline flights, and anything else that's neither military or scheduled airline flying. Please address items (a) through (f) below.

U.S. Manufactured General Aviation Shipments, 1966-2003
Source: U.S. Manufactured General Aviation Shipments, Statistical Databook 2003, General Aviation Manufacturers Association, used with permission.
(a) Prepare a time-series plot of the data for all years.

(b) Describe the pattern and discuss possible causes.

(c) Would a fitted trend be helpful?

(d) Make a similar graph for 1992-2003 only. Would a fitted trend be helpful in making a prediction for 2004?

(e) Fit a straight-line trend model to the 1992-2003 data.

(f) Use either the fitted trend model or common sense and judgment to predict a specific level of sales for 2004.

Why is it best to ignore earlier years in this data set?

Year Planes
1966 15,587
1967 13,484
1968 13,556
1969 12,407
1970 7,277
1971 7,346
1972 9,774
1973 13,646
1974 14,166
1975 14,056
1976 15,451
1977 16,904
1978 17,811
1979 17,048
1980 11,877
1981 9,457
1982 4,266
1983 2,691
1984 2,431
1985 2,029
1986 1,495
1987 1,085
1988 1,143
1989 1,535
1990 1,134
1991 1,021
1992 856
1993 870
1994 881
1995 1,028
1996 1,053
1997 1,482
1998 2,115
1999 2,421
2000 2,714
2001 2,538
2002 2,169
2003 2,090

Solution Summary

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