Class Mark - Formula, Meaning, Examples - Cuemath

Class Mark

Class mark, in statistics, is the average of the upper limit and the lower limit of a class in a frequency distribution. In other words, the class mark is the mid-value of the given class interval.

1.	What is Class Mark?
2.	Class Mark Formula
3.	Class Mark in Frequency Distribution
4.	FAQs on Class Mark

What is Class Mark?

Class mark in a frequency distribution is the midpoint or the middle value of a given class. For example, the class mark of 10-20 is 15, as 15 is the mid-value that lies between 10 and 20. In statistics, the class mark is used at various places, for example, while calculating mean, drawing line graphs, finding the average of each class in a frequency distribution, etc. It is very easy to calculate class mark by using a formula that you will learn in the section below.

Class Mark Formula

The formula to calculate class mark in a frequency distribution is given as (upper limit + lower limit)/2 or (Sum of class boundaries)/2. By using this class mark formula, you can easily find the midpoint of any given class interval.

Let us learn the terms associated with this formula in detail.

Class Interval: It is defined as the size of each class of numerical data in a large frequency distribution following a specific width. For example, if the raw data has too many variations in numbers, we make groups of intervals to organize the data such as 0-10, 10-20, 20-30, etc. These are known as class intervals.

Upper Limit: It is the highest value of the class interval. There could be no item greater than the upper limit in that particular class. For example, the upper limit of 30-40 is 40. It is known as the upper-class boundary.

Lower Limit: It is the lowest value of the class interval. There could be no item less than the lower limit in that particular class. For example, the lower limit of 30-40 is 30. It is known as lower class boundary.

Class Mark in Frequency Distribution

In a histogram (a graphical representation of a frequency distribution), we can easily find the midpoint of each class by observing the values at the x-axis or the horizontal axis. By applying the formula of class mark, let us find the values of class marks for each class in the given distribution showing the salaries of employees working in a company.

Salaries (in $)	Number of Employees	Class Mark (in $)
0-10	50	5
10-20	300	15
20-30	260	25
30-40	400	35
40-50	550	45
50-60	450	55

Let us show this information in a histogram and denote the values of class marks through a dotted line in the middle of each bar representing the range of salaries.

One interesting fact here is that if we join the mid points on the top of each bar, we can draw a line graph.

► Related Articles

Check these interesting topics related to the class mark.

• Frequency Distribution Table
• Measures of Central Tendency
• Line Charts