Suppose that the following are the quarterly sales data for thepast 7 years.
1.Construct a time series plot and develop linear trend equationusing the original data (with seasonal components).
2.Calculate 4-quarter moving average values for this time series(column E).
3.Calculate centered moving average values and seasonal indexes(column F and G).
4.Calculate seasonal indexes (column J) for the fourquarters.
5.Copy seasonal indexes (column J) to column O, and calculatedeseasonalized number sold (column P).
6.Construct a time series plot and develop linear trend equationusing the deseasonalized data (without seasonal components).
Year | Number Sold |
1 | 35 |
2 | 50 |
3 | 75 |
4 | 90 |
5 | 105 |
6 | 110 |
7 | 130 |
Year | Quarter | Number
Sold |
1 | 1 | 6 |
2 | 15 |
3 | 10 |
4 | 4 |
2 | 5 | 10 |
6 | 18 |
7 | 15 |
8 | 7 |
3 | 9 | 14 |
10 | 26 |
11 | 23 |
12 | 12 |
4 | 13 | 19 |
14 | 28 |
15 | 25 |
16 | 18 |
5 | 13 | 22 |
14 | 34 |
15 | 28 |
16 | 21 |
6 | 13 | 24 |
14 | 36 |
15 | 30 |
16 | 20 |
7 | 13 | 28 |
14 | 40 |
15 | 35 |
16 | 27 |
