Question

If the lower and upper limits of a class interval are 7.5 and 12.5, the class interval is_ _ _ _ _ _
A) 12.5-7.5
B) 7.5-12.5
C) Either of A or B
D) None of these

Answer 1

Hint: We need to first understand a class interval before we begin to solve the question. We will first define a class interval and how the upper and lower limits are useful to define it. We also need to clarify that the limits are useful for representing the range of data present in that particular class and it is not the length of the class or the number of elements in the class. We will then represent this concept in a form of an expression as follows, Class Interval is (lower limit-upper limit). Here the sign “-“does not signify mathematical operation of subtraction rather represents the word “to”. Then we will use the given values of 7.5 and 12.5 to correctly represent the class interval in mathematical form.

Complete step by step answer:
Let us start by understanding the concept of Class Interval.
In statistics, when a large number of data is grouped together in different sets to get an idea of the distribution, these groups are called classes.
Class interval is the range of the data that is grouped in a particular class.
For example, let us consider the numbers 1 to 100 are grouped in classes of 10 such that we have class intervals 1-10, 11-20, 21-30 and so on.
In this example the numbers 1 and 10 denote the range of the class.
It clearly tells us the least number is 1 and highest is 10, that is gives us the lower and upper limits for a class.
We can say that the class interval starts from the lower limit and ends at the upper limit.
Therefore, class interval is given by (lower limit-Upper limit), where the sign “-“is used to represent the word “to” for denoting the range.
Now, we will consider the limits given to us in the question.
We have,
Lower limit = 7.5
Upper limit = 12.5
Class interval is given by (lower limit-upper limit)
We will get class interval: 7.5-12.5

So, the correct answer is “Option B”.

Note: In the representation of class interval as lower limit – upper limit, it is important to note that the “– sign” denotes the word “to and not the mathematical operation of subtraction. Also we should not get confused with the length of the class interval which is given by upper limit-lower limit.