A class teacher has the following absentee record of 40 students of a class for the whole term. Find the mean number of days a student was absent.
No. of days
0-6
6-10
10-14
14-20
20-28
28-38
38-40
No. of students
11
10
7
4
4
3
1

12.475

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12.405

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12.005

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12.95

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Solution

The correct option is D 12.475
No. of days (class interval) No. of students Classmark( $X_{i}$ ) $F_{i} X_{i}$
0-6 11 3 33
6-10 10 8 80
10-14 7 12 84
14-20 4 17 68
20-28 4 24 96
28-38 3 33 99
38-40 1 39 39

Total 40 499
We know that Class mark $= \frac{u p p e r l i m i t + l o w e r l i m i t}{2}$

Mean number of days $= \frac{Σ F_{i} X_{i}}{Σ F_{i}} = \frac{499}{40} = 12.475$ Days

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Number of days:	0 − 6	6 − 12	12 − 18	18 − 24	24 − 30	30 − 36	36 − 42
Number of students:	10	11	7	4	4	3	1

Number of days:	0 − 6	6 − 10	10 − 14	14 − 20	20 − 28	28 − 38	38 − 40
Number of students:	11	10	7	4	4	3	1

A class teacher has the following absentee record of 40 students of a class for the whole term. Find the mean number of days a student was absent.

Number of days	0 − 6	6 − 10	10 − 14	14 − 20	20 − 28	28 − 38	38 − 40
Number of students	11	10	7	4	4	3	1

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No. of days	0-6	6-10	10-14	14-20	20-28	28-38	38-40
No. of students	11	10	7	4	4	3	1