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Question
Find the mean of the following frequency distribution :
| Class | 101-110 | 111-120 | 121-130 | 131-140 | 141-150 | 151-160 |
| Frequency | 11 | 16 | 20 | 30 | 14 | 9 |
Solution
| Class Interval | xi | fi | fixi |
| 101-110 | 105.5 | 11 | 1160.5 |
| 111-120 | 115.5 | 16 | 1848 |
| 121-130 | 125.5 | 20 | 2510 |
| 131-140 | 135. | 30 | 4065 |
| 141-150 | 145.5 | 14 | 2037 |
| 151-160 | 155.5 | 9 | 1399.5 |
| Total | 100 | 13020 |
`barx = (Σf_iX_i)/(Σ"f")`
`barx = 13020/100`
`barx = 130.2`
∴ Mean = 130.2
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