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Histograms display grouped continuous data using frequency density (frequency ÷ class width) so area represents frequency. This topic draws and interprets them, including unequal class widths. It's examined right across GCSE and iGCSE Maths. Learn it free on eClassroom through guided worked examples and instantly-marked exam-style questions.
How you do it
The vertical axis is frequency density, which is frequency divided by class width. The area of each bar gives the frequency, not its height. To find the frequency in part of a bar, take that fraction of its area.
Before you start
The prerequisite is grouped frequency and area. It carries straight through to frequency density and comparing distributions. This is a Higher tier topic.
What you learn
When class widths are unequal, a histogram uses frequency density for the bar height so that the area of each bar represents its frequency. With unequal class widths, comparing raw bar heights is misleading. The bars sit on a continuous scale and may be different widths. The modal class is the one with the greatest frequency density — the tallest bar — not necessarily the class with the most items. The course works through frequency density, reading a histogram and modal class and totals. Every section has instant-feedback practice questions matched to Edexcel iGCSE 4MA1 and the other major GCSE boards, and the course finishes with full exam-style questions you mark yourself.
Related Topics
We teach Histograms as one of the Data and Statistics topics in our GCSE course library, at Higher tier. There are 3 teaching sections and 2 fully worked examples, plus 3 sets of check questions. Students often pair it with Types of Data, Averages — Frequency Tables, Averages — Grouped Frequency and Averages — Raw Data. The Data and Statistics revision engine gives you as many extra questions as you want, tracked on your skill tree.
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