Glossary term
Class Mark: Meaning and Definition
Reviewed and approved by Dr. Anamika ShrivastavaPublished Last updated
The class mark is the mid-point of a class in a grouped frequency distribution, found by adding the lower and upper limits and dividing by two. It stands in for all the values in the class when the mean is calculated and when a frequency polygon is drawn.
In more detail
Using the class mark assumes that the values in each class are spread evenly around its middle. That is only approximately true, so the mean of grouped data is slightly different from the mean of the original data. For inclusive classes the class mark is the same whether true boundaries or stated limits are used.
Example
For the class 20–30, the class mark is (20 + 30) ÷ 2 = 25.
Key points
- Class mark = (upper limit + lower limit) ÷ 2.
- Used to find the mean of grouped data.
- Plotted on a frequency polygon.
Common mistake
Using the class width where the class mark is needed.
Related terms
Where it is explained
This term is explained in Class 11 Statistics Chapter 3: Organisation of Data.