Pie Charts are also called Circle Graphs and Sector Graphs. They are best for displaying a small number of discrete categories. A common example is the display of opinion poll results being Yes/No (only two categories).
The procedure for creating a pie chart is:
- Calculate the total.
- Calculate the angle of the circle which is proportional to the sector of the circle, the fraction of the total multiplied by 360 degrees. Round the angle to the nearest whole degree.
- Draw the circle and mark a starting line on the circle. Measure the calculated angle from this starting line and draw the required sector.
- Repeat this process for all categories.
- The total number of degrees does not always add up to 360. This is due to the rounding to the nearest whole degree.
- Ensure that you show all your working as well as the completed circle graph in your answer.
Example - Wildlife Smuggling in Ecuador
Ecuador in South America has a wide biodiversity of colourful birds, but also spends few government funds to stop wildlife smuggling. Below is a table showing the most commonly smuggled animals, most of whom die before reaching their destination. Draw a pie chart of this data.
|SMUGGLED ANIMAL||NUMBER SMUGGLED IN ONE WEEK|
|SMUGGLED ANIMAL||NUMBER SMUGGLED IN ONE WEEK||WORKING||ANGLE|
|Macaw||35||35⁄150 × 360 = 84||84 degrees|
|Jaguar||4||4⁄150 × 360 = 9.6||10 degrees|
|Capuchin monkey||64||64⁄150 × 360 = 153.6||154 degrees|
|Spider monkey||47||47⁄150 × 360 = 112.8||113 degrees|
When 100 people were surveyed as to whether the government should spend more money to prevent wildlife smuggling, the responses were:
- Yes - 34
- No - 45
- Unsure - 21
Draw a pie chart with this information.
Did You Know That...?
Democracy in Ancient Greece where the concept originated was quite different to our contemporary understanding of the term. To be eligible to vote, a person had to be a male born in Athens and over 20 years old. Women and slaves were not permitted to cast their votes.