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 |
|
Fox
Dog
Fox or dog
Other mammal |
|
|
|
|
Bird of prey
Crow
Unknown
|
|
|
|
|
|
|
|
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.