Class Boundaries: Class Boundaries are the midpoints between the upper class limit of a class and the lower class limit of the next class in the sequence. Therefore, each class has an upper and lower class boundary.
| Class | Frequency |
| 200 – 299 | 12 |
| 300 – 399 | 19 |
| 400 – 499 | 6 |
| 500 – 599 | 2 |
| 600 – 699 | 11 |
| 700 – 799 | 7 |
| 800 – 899 | 3 |
| Total Frequency | 60 |
Using the frequency table above, determine the class boundaries of the first three classes.
The lower class boundary is the midpoint between 199 and 200, that is 199.5
The upper class boundary is the midpoint between 299 and 300, that is 299.5
The lower class boundary is the midpoint between 299 and 300, that is 299.5
The upper class boundary is the midpoint between 399 and 400, that is 399.5
The lower class boundary is the midpoint between 399 and 400, that is 399.5
The upper class boundary is the midpoint between 499 and 500, that is 499.5
Class Intervals: Class interval is the difference between the upper and lower class boundaries of any class.
Example:
| Class | Frequency |
| 200 – 299 | 12 |
| 300 – 399 | 19 |
| 400 – 499 | 6 |
| 500 – 599 | 2 |
| 600 – 699 | 11 |
| 700 – 799 | 7 |
| 800 – 899 | 3 |
| Total Frequency | 60 |
Using the table above, determine the class intervals for the first class.
The class interval = Upper class boundary – lower class boundary
Upper class boundary = 299.5
Lower class boundary = 199.5
Therefore, the class interval = 299.5 – 199.5
= 100
