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Question
Find the mean of the following data, using direct method:
| Class | 0-100 | 100-200 | 200-300 | 300-400 | 400-500 |
| Frequency | 6 | 9 | 15 | 12 | 8 |
Solution
| Class | Frequency `(f_i)` | Mid values `(x_i)` | `(f_i xx x_i)` |
| 0-100 | 6 | 50 | 300 |
| 100-200 | 9 | 150 | 1350 |
| 200-300 | 15 | 250 | 3750 |
| 300-400 | 12 | 350 | 4200 |
| 400-500 | 8 | 450 | 3600 |
| `∑f_i =50` | `∑ (f_i xx x_i ) = 13200` |
∴ Mean, x =`(∑ (f_i xx x_i ))/(∑f_i)`
=`13200/50`
=264
∴ x = 264
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