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.

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.

Find the class width or midpoint of a given class interval.

Continue exploring related topics:

• Frequency Tables - Organising Data by Count
• Histograms - Displaying Grouped Continuous Data
• Cumulative Frequency - Running Totals