How to get class boundary

A class boundary is a value that separates two adjacent classes in a frequency distribution. Unlike class limits, class boundaries are continuous, meaning there are no gaps between them. They are used to ensure that data points fall into only one class and are essential for drawing histograms.

To find the class boundary:

• Identify the upper class limit of one class and the lower class limit of the next class.
• The upper class boundary of a class is the midpoint between its upper class limit and the lower class limit of the next class.
• The lower class boundary of a class is the midpoint between its lower class limit and the upper class limit of the preceding class.

Example:
Consider two adjacent classes:
Class 1: $10 - 14$
Class 2: $15 - 19$

The upper limit of Class 1 is 14.
The lower limit of Class 2 is 15.

The upper class boundary for Class 1 (and the lower class boundary for Class 2) is calculated as:

$$\frac{\text{Upper limit of Class 1} + \text{Lower limit of Class 2}}{2} = \frac{14 + 15}{2} = \frac{29}{2} = 14.5$$

So, the class boundary between $10-14$ and $15-19$ is $\boxed{\text{14.5}}$.