The Total solution for NCERT class 6-12
A class teacher hasthe following absentee record of 40 students of a class for the wholeterm. 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
3
1
Solution:
Find the midpoint of the given interval usingthe formula.
Midpoint (xi) = (upper limit +lower limit)/2
Class interval
Frequency (fi)
Mid-point (xi)
fixi
33
8
80
12
84
17
68
24
96
99
39
Sum fi = 40
Sum fixi = 499
The mean formula is,
Mean = x̄ = ∑fixi /∑fi
= 499/40
= 12.48 days
Therefore, the mean number of days a studentwas absent = 12.48.