histogram

A histogram is a frequency diagram which uses the area of each bar to represent frequency.

This means that the frequencies of groups of unequal widths are fairly represented.

Let’s use the information below as an example.

A group of runners hold a sponsored run to raise money for a charity. The first table shows the monetary distribution.

We need to draw a histogram to represent this distribution. In order to do this, two columns must be added to the table – one to note the width of each group, and the other to calculate the frequency distribution using this formula:

    Frequency density = \dfrac{\text{frequency}}{\text{width of group}}

The second table shows the results.

We can now use this information to draw the histogram.