Q) The monthly expenditure on milk in 200 families of a Housing Society is given below:
Find the value of x and also find the mean expenditure
Ans:
(i) Value of X:
To calculate the value of X, we first sum up all the frequencies:
Here, from 2nd column, we get total number of families = 172 + X
In the question, it is given that the total number of families = 200
∴ 172 + X = 200
∴ X = 200 – 172 = 28
Therefore, the value of X is 28.
(ii) Mean value of expenditure:
To find the mean value, we put X = 28 in the table and rearrange the data:
To re-arrange the above data, we take the following steps:
- We calculate midpoint ‘x’ of each class by
- Then we calculate ‘fx’ by multiplying midpoint of each class with frequency of that class
- We calculate Σf by summing up all the frequencies and Σfx by adding up all the values of fx
Next, we know that, mean of grouped data is given by:
Mean of grouped data = 
Therefore, Mean value = 
= 2,662.50
Hence, the mean value of the given data is 2,662.50
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