Statistics · Data representation
Chapter 1 · 4
The idea
Bar charts & pie charts
Why a bar chart carries the frequency in its height while a pie chart carries only the share in its angle — so two identical-looking pies can stand for wildly different numbers — and how to convert between frequency and angle both ways.
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 · Data representation
Bar charts & pie charts
Why a bar chart carries the frequency in its height while a pie chart carries only the share in its angle — so two identical-looking pies can stand for wildly different numbers — and how to convert between frequency and angle both ways.
Why it works
The measurement carries the number
A chart is a frequency table redrawn so that something you can see carries the number. Which measurement does the carrying — a height, a slice of a circle — and what it is compared against, is the whole subject. Read the wrong measurement and a perfectly honest picture will hand you a false fact.A bar chart: height is the frequency
Categories along the bottom, one bar each, equal widths, gaps between. Width means nothing here, so the bars differ only in the one way that does mean something — height. The gaps matter: the axis is a list of labels, not a number line, so the bars must not touch. (That gap is the line between a bar chart and a histogram, where bars touch and area carries the frequency.)Keep reading — free
The rest of the explanation, plus 3 worked examples you step through move by move.
Start freeTakes a minute — no card.