Please solve example 4 by shortcut method
Let assumed mean be A = 17
| xi | fi | di = xi − A = xi − 17 | di2 | fidi | fidi2 |
| 4 | 3 | −13 | 169 | −39 | 507 |
| 8 | 5 | −9 | 81 | −45 | 405 |
| 11 | 9 | −6 | 36 | −54 | 324 |
| 17 | 5 | 0 | 0 | 0 | 0 |
| 20 | 4 | 3 | 9 | 12 | 36 |
| 24 | 3 | 7 | 49 | 21 | 147 |
| 32 | 1 | 15 | 225 | 15 | 225 |
| N = 30 | ∑fidi = −90 | ∑fidi2 = 1644 |