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Solution - A class teacher has the following absentee record of 40 students of a class for the whole term. - CBSE Class 10 - Mathematics

ConceptMean of Grouped Data

Question

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

 

Solution

 

To find the class mark of each interval, the following relation is used.

`x_i  = ("Upper class limit + Lower class limit")/2`

Taking 17 as assumed mean (a), di and fidi are calculated as follows.

Number of days

Number of students

fi

Mid value(xi) di xi − 17 fidi
0 − 6 11 3 − 14 − 154
6 − 10 10 8 − 9 − 90
10 − 14 7 12 − 5 − 35
14 − 20 4 17 0 0
20 − 28 4 24 7 28
28 − 38 3 33 16 48
38 − 40 1 39 22 22
  40     − 181

From the table, we obtain

`sumf_i = 40`

`sumf_iu_i = -181`

`"Mean " barx = a+ ((sumf_iu_i)/(sumf_i))xxh`

`= 17 + ((-181)/40)`

= 17 - 4.525

= 12.475

=12.48

Therefore, the mean number of days is 12.48 days for which a student was absent.

 
Is there an error in this question or solution?

APPEARS IN

 NCERT Mathematics Textbook for Class 10 (with solutions)
Chapter 14: Statistics
Q: 8 | Page no. 272

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Reference Material

Solution for question: A class teacher has the following absentee record of 40 students of a class for the whole term. concept: Mean of Grouped Data. For the course CBSE
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