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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. - Mathematics

Sum

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 6-12 12-18 18-24 24-30 30-36 36-42
Number of students: 10 11 7 4 4 3 1
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Solution

We will do it by a direct method

Using: mean`(∑ "f"_"i""x"_"i")/(∑ "f"_"i")`

Number of days   Number of students 
(fi)
Classmark 
(xi)
fixi
0-6 10 `(0+6)/2 = 3` 30
6-12 11 `(6+12)/2 = 9` 99
12-18 7 `(12+18)/2 =15` 105
18-24 4 `(18+24)/2 = 21` 84
24-30 4 `(24+30)/2 =27` 108
30-36 3 `(30+46)/2 =33` 99
36-42 1 `(36+42)/2 = 39` 39
  ∑ fi = 40   ∑ fixi =564

substituting the values in the formula

mean = `564/40 = 14.1`

Concept: Mean of Grouped Data
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