Question 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.
Expenditure (in Rs)Number of families1000−1500241500−2000402000−2500332500−3000283000−3500303500−4000224000−4500164500−50007
From the given data, maximum class frequency is 40 belonging to 1500 - 2000 interval.
So, modal class = 1500 - 2000
Lower limit l of modal class = 1500
Frequency (f1) of modal class = 40
Frequency (f0) of class preceding modal class = 24
Frequency (f2) of class succeeding modal class = 33
Class size h = 500
Mode=l+(f1−f02f1−f0−f2)×h=1500+(40−242(40)−24−33)×500=1500+(1680−57)×500=1500+800023
= 1500 + 347.826
= 1847.826 = 1847.83
So, modal monthly expenditure was Rs.1847.83
Now, to calculate mean :
we may find class mark as;
Class mark=upper class limit+lower class limit2
Class size h of given data = 500
Now, taking 2750 as assumed mean a we may calculate di,ui and fiui as following:
Expenditure (in Rs)Number of families fixidi=xi−2750ui=xi−2750hfiui1000−1500241250−1500−3−721500−2000401750−1000−2−802000−2500332250−500−1−332500−30002827500003000−35003032505001303500−400022375010002444000−450016425015003484500−5000747502000428Total200 −35
Now, from the table it may be observed that:
∑fi=200∑fiui=−35¯x(mean)=a+(∑fiui∑fi)×h¯x=2750+(−35200)×500
= 2750 - 87.5
= 2662.5
So, the mean monthly expenditure was Rs.2662.50.