Bar charts

Although a frequency table itself provides a useful description of a categorical distribution, a graphical display of the frequencies is often easier to absorb. The main graphical display of categorical data is a bar chart.

Bar charts for categorical data are similar to those that were described earlier for discrete data. For each distinct category, a bar is drawn with height equal to the frequency (or equivalently relative frequency) of that category.

Kestrel causes of death

The bar chart below shows the causes of death of kestrels in Britain between 1963 and 1997, based on carcasses sent to the researchers in response to advertisements in bird-watching magazines and journals.

Clicking on any bar highlights it and the corresponding values on the frequency table.

Note that the bar chart is shown with both a frequency axis (on the left) and a proportion axis (on the right). It has the same shape whichever is used.