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Histograms
Histograms show grouped data with unequal class widths. The area of each bar, not its height, shows the frequency.
Frequency density
frequency density = frequencyclass width
The height of each bar is the frequency density.
The height of each bar is the frequency density.
Finding frequencies
frequency = frequency density × class width, which is the area of the bar.
Example
A bar has frequency density 4 and class width 15. Find the frequency.
- frequency = 4 × 15
Answer: 60
Frequency density = frequency ÷ class width, and is the bar's height. Frequency = density × width, which is the bar's area.
The interactive lesson includes the diagrams for this topic.
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