Class limit, boundary, interval, width and midpoint
Class Limits
Class limits are the smallest and largest observations (data, events etc) in each class. Hence, each
class has two limits: a lower and upper limit.
Example:
Class
Frequency
300 โ 399
13
400 โ 499
20
500 โ 599
7
600 โ 699
3
700 โ 799
12
800 โ 899
8
900 โ 999
7
Total Frequency
70
By means of the frequency table above, what are the lower and upper class limits for the first three
classes? One can definitely see that;
For the first class, 300 โ 399
The lower class limit is 300
The upper class limit is 399
For the second class, 400 โ 499
The lower class limit is 400
The upper class limit is 499
For the third class, 500 โ 599
The lower class limit is 500
The upper class limit is 599
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. It is 0.5 more or less of a class limit. Therefore, each class has an
upper and lower class boundary.
Example:
Class
Frequency
300 โ 399
13
400 โ 499
20
