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प्रश्न
The number of students absent in a class were recorded every day for 120 days and the information is given in the following frequency table:
| No. of students absent (x) | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| No. of days (f) | 1 | 4 | 10 | 50 | 34 | 15 | 4 | 2 |
Find the mean number of students absent per day.
उत्तर
Let the assumed mean (A) = 3
| No. of students absent x1 |
No. of days f1 |
u1 = x1 - A x1 - 3 |
f1u1 |
| 0 | 1 | -3 | -3 |
| 1 | 4 | -2 | -8 |
| 2 | 10 | -1 | -10 |
| 3 | 50 | 0 | 0 |
| 4 | 34 | 1 | 34 |
| 5 | 15 | 2 | 30 |
| 6 | 4 | 3 | 12 |
| 7 | 2 | 4 | 8 |
| N = 120 | `sumf_1"u"_1=63` |
Mean number of students absent per day `=A+(sumf_1"u"_1)/N`
`=3+63/120`
`=(360+63)/120`
`=423/120`
= 3.525
= 3.53(Approx)
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| 33 - 35 | 9 |
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