Q2 of 33 Page 14

New Page 2 Find the mean marks from the following data:

Marks Number of Students
Below 10
Below 20
Below 30
Below 40
Below 50
Below 60
Below 70
Below 80
Below 90
Below 100		 5
9
17
29
45
60
70
78
83
85 

 

MarksNumber of Students (fi)Mid-point (xi)Deviation
ui =(xi - 55)/10		fiui
0 - 105 5-5-25
10 - 209 - 5 = 4 15-4-16
20 - 3017 - 9 = 8 25-3-24
30 - 4029 - 17 = 1235-2-24
40 - 5045 - 29 = 1645-1-16
50 - 6060 - 45 = 15a = 5500
60 - 7070 - 60 = 1065110
70 - 8078 - 70 = 875216
80 - 9083 - 78 = 585315
90 - 10085 - 83 = 29548
Total85  -56

Hence mean = a + h ×  [where h = 10]                           = 55 + 10 ×  = 48.41 marks

More from this chapter

All 33 →
1 The following table shows marks secured by 140 students in an examination:


Marks 0-10 10-20 20-30 30-40 40-50
    Number of      students 20 24 40 36 20


Calculate mean marks by using all the three methods, i.e., direct method, assumed mean method and step-deviation method. 3  New Page 2 Find the mean age of 100 residents of a colony from the following data:



Age in years (Greater than or equal to) Number of Persons
0 10 20 30 40 50 60 70 100 90 75 50 25 15 5 0 

4 If the mean of the following data is 21.5, find the value of k:
          
xi 5 15 25 35 45
fi 6 4 3 k 2
5 Find the values of f1 and f2 of the frequency, if the mean of the following frequency distribution is 21.4 and the total frequency is 40.
Class-interval 0 - 8 8 - 16 16 - 24 24 - 32 32 - 40
Frequency 6 f1 10 f2 9