Question

Explain the meaning of the terms: class-interval.

Answer 1

Hint:
Here we have to explain the meaning of class-interval. So we will first give the proper definition of the class interval and then we will take the example with proper distribution of data. Then we will calculate the class interval by using its formula and then we will explain the uses of the formula of class interval here.

Complete step by step solution:
Let’s first define the term class interval.
Class interval is defined as the range in which data are grouped while arranging them in statistics and it is also defined as the difference of upper class limit and the lower class limit.
Generally, class intervals are of equal width. Formula for calculating class interval is given by, class interval \[ = \] upper class limit \[ - \] lower class limit
We will now take one example to understand it better.
The following data are the ages of randomly selected 10 students of a school.
8, 9, 11, 13, 13, 16, 17, 18
Now, we will group the data.

Class interval	Frequency
\[5 - 10\]	\[2\]
\[10 - 15\]	\[3\]
\[15 - 20\]	\[3\]

Here the class interval \[ = 10 - 5 = 15 - 10 = 20 - 15 = 5\]
Therefore the class interval is 5.
In the first row, the upper class limit is 10 and lower class limit is 5.
So the difference of upper and lower class limit is 5 which is the class interval we have calculated.
Note:
Generally, class intervals are of equal widths and they are mutually exclusive also. Class intervals are generally used in histogram for grouping of data. The midpoint of the class interval is the class mark. An inclusive series is the one where the class intervals include both upper limit and lower limits. For example: In the inclusive series in the example given, 10 – 19 includes all the numbers between 10 and 19, including 10 and 19 also.
An exclusive series is the one where the class intervals include both upper limit and lower limits. In an exclusive series, the upper limit of a class interval is equal to the lower limit of the next class interval. For example: In the exclusive series in the example given, \[9.5\] – \[19.5\] includes all the numbers between \[9.5\] and \[19.5\], including \[9.5\] but not \[19.5\].