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The following data gives the distribution of total monthly household expenditure of 200 families of a village. Find the modal monthly expenditure of the families. Also, find the mean monthly expenditure :

3.   The following data gives the distribution of total monthly household expenditure of 200 families of a village. Find the modal monthly expenditure of the families. Also, find the mean monthly expenditure :

       2.3

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The class having maximum frequency is the modal class.

The maximum frequency is 40 and hence the modal class = 1500-2000

Lower limit (l) of modal class = 1500, class size (h) = 500

Frequency ( f_1 ) of the modal class = 40 frequency ( f_0 ) of class preceding the modal class = 24, frequency ( f_2 ) of class succeeding the modal class = 33.

Mode = l + \left(\frac{f_1-f_0}{2f_1 - f_0 - f_2} \right).h

\\ = 1500 + \left(\frac{40-24}{2(40)-24-33} \right).500 \\ \\ = 1500 + \frac{16}{23}.500

= 1847.82

Thus, Mode of the data is Rs. 1847.82

Now,

Let the assumed mean be a = 2750 and h = 500

Expenditure

Number of

families f_i

Class mark

x_i

d_i = x_i -a u_i = \frac{d_i}{h} f_iu_i
1000-1500 24 1250 -1500 -3 -72
1500-2000 40 1750 -1000 -2 -80
2000-2500 33 2250 -500 -1 -33
2500-3000 28 2750 0 0 0
3000-3500 30 3250 500 1 30
3500-4000 22 3750 1000 2 44
4000-4500 16 4250 1500 3 48
4500-5000 7 4750 2000 4 28
 

\sum f_i

=200

     

\sum f_ix_i

= -35

Mean, 

\overline x =a + \frac{\sum f_iu_i}{\sum f_i}\times h 
= 2750 + \frac{-35}{200}\times500 = 2750 -87.5 = 2662.50

Thus, Mean monthly expenditure is Rs. 2662.50 

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