Statistics · Cumulative frequency & box plots
Chapter 1 · 3
The idea
Cumulative frequency diagrams
How to build a running total from a grouped frequency table, why every point is plotted at the upper class boundary rather than the midpoint, and how to read estimates off the curve in both directions.
A full journey — read it, play with it, work it, then earn real exam marks. Everything stays on the timeline below.
In this lesson — start anywhere
Statistics · Cumulative frequency & box plots
Cumulative frequency diagrams
How to build a running total from a grouped frequency table, why every point is plotted at the upper class boundary rather than the midpoint, and how to read estimates off the curve in both directions.
Why it works
A running total
An ordinary grouped frequency table tells you how many values fall inside each class. A cumulative frequency table answers a different question: how many values are at or below a given point? You build it by keeping a running total, adding the classes on from the bottom.Here are the ages, in years, of the 60 members of a swimming club.
| Age, (years) | Frequency | Cumulative frequency |
|---|---|---|
| 6 | 6 | |
| 14 | 20 | |
| 20 | 40 | |
| 13 | 53 | |
| 7 | 60 |
Keep reading — free
The rest of the explanation, plus 3 worked examples you step through move by move.
Start freeTakes a minute — no card.