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प्रश्न
The mean of the following distribution in 52 and the frequency of class interval 30-40 'f' find f
| C.I | 10-20 | 20-30 | 30-40 | 40-50 | 50-60 | 60-70 | 70-80 |
| freq | 5 | 3 | f | 7 | 2 | 6 | 13 |
उत्तर
| C.I | Frequency (f) | Mid value (x) | fx |
| 10-20 | 5 | 15 | 75 |
| 20-30 | 3 | 25 | 75 |
| 30-40 | f | 35 | 35f |
| 40-50 | 7 | 45 | 315 |
| 50-60 | 2 | 55 | 110 |
| 60-70 | 6 | 65 | 390 |
| 70-80 | 13 | 75 | 975 |
| Total | 36+f | 1940+35f |
Mean= `(∑ fx)/(∑ f) =(1940+35f)/(36+f)` .....(1)
But, mean =52 .........(2)
From (1) and (2)
`(1940+35f)/(36+f)=52`
1940 + 35f = 1872 + 52f
17f = 68
f = 4
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