Q3 of 33 Page 14

 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 

 

Age Number of Persons (fi)Mid-point (xi)Deviation
ui= (xi - 35)/10		fiui
0 - 10100 - 90 = 105 -3-30
10 - 2090 - 75 = 1515-2-30
20 - 3075 - 50 = 2525-1-25
30 - 4050 - 25 = 25a = 3500
40 - 5025 - 15 = 1045110
50 - 6015 - 5 = 1055220
60 - 705 - 0 = 565315
Total100  -40
Hence mean = a + h  ×    [where h = 10]                       = 35 + 10  × = 31 years

More from this chapter

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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. 2 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 
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