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Question
Find the mean of the following frequency distribution :
| class | 0-6 | 6-12 | 12-18 | 18-24 | 24-30 |
| Frequency | 7 | 5 | 10 | 12 | 6 |
Solution
| Class Interval | Xi | fi | fiXi |
| 0-6 | 3 | 7 | 21 |
| 6-12 | 9 | 5 | 45 |
| 12-18 | 15 | 10 | 150 |
| 18-24 | 21 | 12 | 252 |
| 24-30 | 27 | 6 | 162 |
| Total | 40 | 630 |
`barx = (Σf_iX_i)/(Σ"f")`
`barx = 630/40`
`barx = 15.75`
∴ Mean = 15.75
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