In a frequency distribution, class width refers to the difference between the upper and lower boundaries of any class or category. It is calculated as:
[tex]Width=\frac{greatest-lowest}{n}=\frac{65-45}{7}=2.85[/tex]
Where "greatest" and "lowest" are the greatest and the lowest numbers of the whole set of data, and "n" is the number of classes. Hence, the class width is 2.85
