Question: Use the sales data given below to determine: (a) the least squares trend line, and (b) the predicted value for 2003 sales.
| Year | Sales (Unit) |
| 1996 | 100 |
| 1997 | 110 |
| 1998 | 122 |
| 1999 | 130 |
| 2000 | 139 |
| 2001 | 152 |
| 2002 | 164 |
Solution:
| Year | Time Period (X) | Sales (Units) (Y) | X2 | XY |
| 1996 | 1 | 100 | 1 | 100 |
| 1997 | 2 | 110 | 4 | 220 |
| 1998 | 3 | 122 | 9 | 366 |
| 1999 | 4 | 130 | 16 | 520 |
| 2000 | 5 | 139 | 25 | 695 |
| 2001 | 6 | 152 | 36 | 912 |
| 2002 | 7 | 164 | 49 | 1148 |
| ∑X = 28 | ∑Y = 917 | ∑X2 = 140 | ∑XY = 3961 |
