Statistics And Probability Question 400

Question: In the following frequency distribution. Class limits of some of the class intervals and mid-vale of a class are missing. However, the mean of the distribution is known to be 46.5.
Class intervals Mid-values Frequency
$x_1-x_2$ 15 10
$x_2-x_3$ 30 40
$x_3-x_4$ M 30
$x_4-x_5$ 75 10
$x_5-100$ 90 10

The values of $ x_1,x_2,x_3,x_4,x_5 $ respectively will be

Options:

A) $ (0,20,40,60,80) $

B) $ (40,50,60,70,80) $

C) $ (10,20,40,70,80) $

D) $ (0,19.5,39.5,69.5,80) $

Show Answer

Answer:

Correct Answer: C

Solution:

[c] $ \frac{\Sigma x_{i}f_{i}}{\Sigma f_{i}}=46.5 $
$ \Rightarrow \frac{15\times 10+30\times 40+M\times 30+75\times 10+90\times 10}{10+40+30+10+10}=46.5 $
$ \therefore M=55. $ so the class intervals can be $ 10-20,20-40,40-70,70-80,80-100 $