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प्रश्न
Find the mean of each of the following frequency distributions
| Classes | 25 - 29 | 30 - 34 | 35 - 39 | 40 - 44 | 45 - 49 | 50 - 54 | 55 - 59 |
| Frequency | 14 | 22 | 16 | 6 | 5 | 3 | 4 |
उत्तर
Let the assume mean A = 42
| Classes | Mid value(x1) | d1 = x1 - 42 | `"u"_1=(x1-42)/5` | f1 | f1u1 |
| 25 - 29 | 27 | -15 | -3 | 14 | -42 |
| 30 - 34 | 32 | -10 | -2 | 22 | -44 |
| 35 - 39 | 37 | -5 | -1 | 16 | -16 |
| 40 - 44 | 42 | 0 | 0 | 6 | 0 |
| 45 - 49 | 47 | 5 | 1 | 5 | 5 |
| 50 - 54 | 52 | 10 | 2 | 3 | 6 |
| 55 - 59 | 57 | 15 | 3 | 4 | 12 |
| N = 70 | `sumf_1"u"_1=-79` |
We have
A = 42, h = 5
Mean `=A+hxx(sumf_1"u"_1)/N`
`=42+5xx(-79)/70`
`=42+(-395)/70`
`=42-395/70`
= 42 - 5.643
= 36.357
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