Data Handling and Statistics
Grouped Frequency Tables
When data is continuous or spread across a wide range, we group it into class intervals instead of listing every single value. For example, heights might be grouped as 140–149, 150–159, 160–169.
Class Width and Midpoint
The class width is the size of the interval: (upper boundary − lower boundary) + 1. For 140–149, the width is (149 − 140) + 1 = 10.
The midpoint is the centre of the interval, used to represent all the values inside it: (lower + upper) ÷ 2. For 140–149, the midpoint is (140 + 149) ÷ 2 = 144.5.
Practice: Class Width and Midpoint
Find the class width or midpoint of a given class interval.