Class mid-values of a frequency distribution of marks in economics of a group of students in Class XI are given as 25,32,39,46,53 and 60.
Find the size of the class interval and class limits.

Explanation

Size of class interval = Mutual difference between mid-values
=32-25=39-32 = 46-39= .....60-53
=7
Thus, the size of the class is 7.
Given the size of the class as 7 and mid-values of classes as 25, 32, 39, 46, 53 and 60, we can now obtain the class limits by using the following formulae:
Lower limit: `l_1=m-1/2i`
Upper limit: `l_2=m+1/2i`
where, m=mid-values, i = difference between mid-values or the size of class.
Accordingly, the class limits of the first class will be :
`l_1=25-1/2xx7-25-3.5-21.5`
`l_2=25+1/2xx7=25+3.5=28.5`
and so on.
Thus, the various classes with class limits are given as :