Bar charts and pie charts highlight different aspects of the data

Although a bar chart and a pie chart are visual representations of the same values (the proportions in the categories), they highlight different features of these proportions.

Bar charts provide better comparisons of the individual proportions, whereas pie charts allow us to assess the proportions in two or more adjacent categories.

Predators and free-range poultry

Data were collected in the east of France to assess the main predators of free-range poultry. Typically the chickens are given free access to fields surrounding their hen house for a period of 9-23 weeks, usually returning to the hen house at night. The main predators are birds of prey (raptors), crows, foxes and dogs.

Although the predators were usually not sighted, the type of predator could usually be inferred from the wounds on the chicken bodies and feathers, hair or droppings around the bodies. The table below shows the numbers of birds that were killed during the study.

Class Predator Frequency Percentage
Mammal
Fox
Dog
Fox or dog
Other mammal
176
157
231
65
19
17
25
7
Bird
Bird of prey
Crow
Unknown
93
37
102
10
4
11
Unknown
Unknown
64
7
Total  
925
100

A pie chart and a bar chart are shown below.

The bar chart shows that fewer chickens were positively identified as killed by dogs than foxes. This is less obvious from the pie chart. Click on the categories to read off the exact proportions.

On the other hand, the pie chart shows that about two thirds of the chickens were killed by mammals (fox, dog, 'fox or dog' and 'other mammal') since these categories span about two thirds of the circle. This information is not immediately apparent in the bar chart. Drag over adjacent categories to read off the proportion of these predators.