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Question
The following table gives the age of 50 student of a class. Find the arithmetic mean of their ages.
| Age-years | 16 – 18 | 18 – 20 | 20 – 22 | 22 – 24 | 24 – 26 |
| No. of students | 2 | 7 | 21 | 17 | 3 |
Solution
| Age in years C.I. |
`x_i` | Number of student (`f_i`) |
`x_i f_i` |
| 16 – 18 | 17 | 2 | 34 |
| 18 – 20 | 19 | 7 | 133 |
| 20 – 22 | 21 | 21 | 441 |
| 22 – 24 | 23 | 17 | 391 |
| 24 – 26 | 25 | 3 | 75 |
| Total | 50 | 1074 |
`barx = (f_ix_i)/(sumf)`
= `1074/50`
= 21.48
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