Pie charts A pie chart is a circular graph (360°) that shows the proportion that different categories contribute to an overall total.
Pie charts are particularly useful for representing categorical data. They cannot be used for continuous data.
In this pie chart, you can clearly see that romance was the most popular type of movie of the people questioned because it has the largest sector area. Drama was the least favourite type of movie because it has the smallest sector area.
Drawing a pie chart Find the total number surveyed.
1 3
Work out the angle for each category by multiplying the fraction by 360°.
The angle in a full circle is 360°. 5
By the end of this section you should be able to: ● draw and interpret pie charts ● draw and interpret stem and leaf plots
● decide the most appropriate graph to represent data
Favourite type of movie Sci-fi
Comedy Drama Romance Action
2 4
Represent each category as a fraction of the total.
Mark a centre, use a compass to draw a circle and a start line from the centre to one side of the circle.
Use a protractor placed on the start line to begin measuring each of the angles around the circle. Each line drawn becomes the start line for the next angle.
Worked example 1 Represent the following data on a pie chart.
Favourite sport Gaelic football Hurling Basketball Rugby Football No. of students