1. For the data of Exercise:
a. Obtain the centered moving average for N 5 4; for N 5 12.
b. When N 5 12 months, the centered moving average is relatively smooth compared to when N 5 4. Aside from the fact that it includes a greater number of months at a time, is there any other reason why the moving average with N 5 12 should be so smooth?
2. The following data describe the monthly volume for an urban courier service. Data are in thousands of pieces handled.
|
|
J
|
F
|
M
|
A
|
M
|
J
|
|
2007
|
4.5
|
4.7
|
4.7
|
5.0
|
5.0
|
4.4
|
|
2008
|
5.4
|
4.9
|
5.3
|
5.6
|
5.4
|
5.4
|
|
2009
|
5.8
|
5.8
|
6.6
|
6.5
|
6.2
|
6.7
|
|
|
J
|
A
|
S
|
O
|
N
|
D
|
|
2007
|
4.7
|
4.9
|
4.6
|
5.4
|
4.8
|
5.2
|
|
2008
|
5.5
|
5.4
|
5.7
|
6.3
|
5.3
|
6.3
|
|
2009
|
6.7
|
6.7
|
6.9
|
7.4
|
6.6
|
7.4
|
a. Construct a graph of the time series. Does the overall trend appear to be upward or downward?
b. Determine the three-month and five-month centered moving average curves and superimpose each on the original time series.
a. Construct a graph of the time series. Does the overall trend appear to be upward or downward?
b. Determine the three-year and five-year centered moving average curves and superimpose each on the original time series.