In: Statistics and Probability
The following data represent a company's yearly sales volume and its advertising expenditure over a period of 8 years.
|
Advertising (x) |
Sales (y) |
|
400,000 |
6,000,000 |
|
500,000 |
7,200,000 |
|
500,000 |
8,000,000 |
|
660,000 |
7,500,000 |
|
790,000 |
8,900.000 |
|
540,000 |
8,100,000 |
|
420,000 |
5,900.000 |
|
380,000 |
4,000,000 |
| X | Y | XY | X^2 | Y^2 |
| 400,000 | 6,000,000 | 2.4E+12 | 1.6E+11 | 3.6E+13 |
| 500,000 | 7,200,000 | 3.6E+12 | 2.5E+11 | 5.184E+13 |
| 500,000 | 8,000,000 | 4E+12 | 2.5E+11 | 6.4E+13 |
| 660,000 | 7,500,000 | 4.95E+12 | 4.36E+11 | 5.625E+13 |
| 790,000 | 8,900.00 | 7.03E+09 | 6.24E+11 | 79210000 |
| 540,000 | 8,100,000 | 4.37E+12 | 2.92E+11 | 6.561E+13 |
| 420,000 | 5,900.00 | 2.48E+09 | 1.76E+11 | 34810000 |
| 380,000 | 4,000,000 | 1.52E+12 | 1.44E+11 | 1.6E+13 |

From the above table and formula we get the value are as;
| n | 8 |
| sum(XY) | 20853509000000 |
| sum(X) | 4190000.00 |
| sum(Y) | 40814800.00 |
| sum(X^2) | 2332100000000.00 |
| sum(Y^2) | 289700114020000 |
| b | -3.802980 |
| a | 7093660.7341 |
ycap = a + bx
ycap = 7093660.7341 - 3.802980x
when x = 315000
The best predicted sales =
7093660.7341 - 3.802980 * 315000
= 5895722.0
ycap = 7093660.7341 - 3.802980 * 315000
when ycap = 9500000
9500000 = 7093660.7341 - 3.802980 * x
3.802980 * x = 7093660.7341 - 9500000
x = -632751