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GCSE Mathematics · key term
The frequency per unit of class width, calculated by dividing frequency by class width.
Used by AQA, Edexcel and OCR
Specification S3 · Paper 1, Paper 2, Paper 3
The frequency of a class divided by its class width; it gives the height of a histogram bar.
Revise: Histograms and Cumulative FrequencyDraw a touching bar across each interval, at its calculated density; label the vertical axis frequency density.
Specification S3, S4 · Paper 1, Paper 2, Paper 3
Revise: Grouped and Continuous DataWhen all classes have the same width, frequencies and frequency densities differ only by a constant scale factor, so a frequency scale can be used. Frequency density is essential when the widths are unequal and is the reliable general method.
Frequency density is the frequency per unit of class width; it determines the height of a histogram bar.
Specification 12.02b · Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Foundation), Paper 4 (Higher), Paper 5 (Higher), Paper 6 (Higher)
Revise: Histograms and Cumulative FrequencyLabel the vertical axis Frequency density.
For unequal class widths, calculate frequency density before drawing a histogram; bar height is not frequency.
To recover a frequency from a histogram, multiply the bar’s frequency density by its class width.
For an unequal-width histogram, never use frequency as the bar height. Calculate frequency density for every class.
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