Question

Define the following term: Class interval

Answer 1

Hint: In this question, we have to define the term 'class interval'. So we will first understand the meaning of class intervals. After that, we will state its formula and then understand the concept with the help of an example. At last, we will give a proper definition of the term 'class interval'.

Complete step-by-step solution:
The class interval is a term used in statistics when we are given a continuous series. Class means a group of numbers in which items are placed such as 0-10, 10-20, 20-30, etc. Class interval refers to the numerical width of any class in a particular distribution.
Mathematically it is defined as the difference between the upper-class limit and the lower class limit.
Class interval = upper-class limit - lower class limit.
In statistics, the data is arranged into different classes and the width of such classes is called a class interval. Class intervals in a particular distribution are generally equal in width but this might not be the case always. Classes are generally mutually exclusive.
Class intervals are very useful in drawing histograms.
Let us understand the meaning of class interval using the following example:
Here, we are given the following data and we have to group them into classes and find class intervals.
8, 19, 58, 35, 45, 12, 6, 13, 18, 47.
As we can see, the lowest term is 6 and the highest term is 58, so we can group the data by 0-10, 10-20, 20-30, 30-40, 40-50, 50-60.
So let us draw a frequency distribution table:

Class	Frequency
0-10	2
10-20	4
20-30	0
30-40	1
40-50	2
50-60	1

Here, we can see, classes are 0-10, 10-20, 20-30, 30-40, 40-50, 50-60.
Let us calculate class intervals for given classes.
As we know, class interval = upper limit - lower limit.
So, for 0-10, upper limit = 10 and lower limit = 0.
Hence, class interval = 10-0 = 10.
Similarly, for all classes, 10-20, 20-30, 30-40, 40-50, 50-60.
$$\text{Class interval}=20-10=30-20=40-30=50-40=60-50=10$$.
The grouping of the above questions can be done differently with different class intervals also. Such as 0-20, 20-40, 40-60 where class interval will be 20.
Hence, we have concluded that,
Classes are the subset into which the data is grouped and class intervals are the width of classes calculated by taking the difference between upper-class limit and lower class limit.

Note: Students should learn the definition of all terms used in statistics. They should not get confused between class, class interval, classmark, and class limits. Class is the subset in which data is grouped, the class interval is the width of that class, classmark is the midpoint of that class, and class limits are upper and lower limits of the class.