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Question
Find the mean of the following data, using direct method:
| Class | 25-35 | 35-45 | 45-55 | 55-65 | 65-75 |
| Frequency | 6 | 10 | 8 | 12 | 4 |
Solution
| Class | Frequency`(f_i)` | Mid values`(x_i)` | `(f_i xx x_i)` |
| 25-35 | 6 | 30 | 180 |
| 35-45 | 10 | 40 | 400 |
| 45-55 | 8 | 50 | 400 |
| 55-65 | 12 | 60 | 720 |
| 65-75 | 4 | 70 | 280 |
| ∑`f_1 = 40` |
`∑ (f_i xx x_i)=1980` |
∴ Mean , x = `(∑ (f_i xx x_i)) /(∑f_1)`
=`1980/40`
=49.5
∴ x = 49.5
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