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.
Let the assumed mean (A) = 3
No. of students absent (xi) | No. of days (fi) | ui = xi – A = xi - 3 | fiui |
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 | ∑fiui = 63 |
Mean number of students absent per day = A + 
= 3 + 
= 
= 3.53 (approx)
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