Method

Drawing a Pie Chart

A pie chart is an effective way of visualizing the proportions of different groups of data when compared to a whole. Pie charts are divided into slices, each of which represents a group and its relative frequency. The central angle of each slice can be found by multiplying each relative frequency by 360^(∘). Central Angle = Relative Frequency * 360^(∘) As an example, consider a survey of a group of people's favorite ice cream flavors. Suppose that 20 people took part in the survey. Eight people responded that they prefer chocolate, six prefer vanilla, and six prefer other flavors. The following steps can be used to create a pie chart representing this survey.

Make a Frequency Table

Begin by identifying each group of the survey. In this case, there are three different flavor groups: chocolate, vanilla, and other. These three groups have eight, six, and six people, respectively.

Flavor	Frequency
Chocolate	8
Vanilla	6
Other	6

Find the Relative Frequency of Each Group

A total of 20 people took part of the survey, so each frequency will be divided by this value to find the relative frequency of each group.

Flavor	Frequency	Relative Frequency
Chocolate	8	8/20 = 0.4
Vanilla	6	6/20 = 0.3
Other	6	6/20 = 0.3

Find the Central Angle of Each Slice

To find the central angle of each slice multiply the relative frequency of its group by 360^(∘). Central Angle = Relative Frequency * 360^(∘) This needs to be done for every different group of the survey.

Flavor	Frequency	Relative Frequency	Central Angle
Chocolate	8	0.4	0.4* 360^(∘) = 144^(∘)
Vanilla	6	0.3	0.3* 360^(∘) =108^(∘)
Other	6	0.3	0.3* 360^(∘) =108^(∘)

Draw the Slices

Begin by drawing a circle to represent the whole population of the survey.

Next, draw a radius to select a starting point. This can be any radius of the circle.

Align the protractor with the starting radius and mark the central angle corresponding to the first group, which is 144^(∘).

Draw the radius that passes through the previous mark. The slice of the first group is now ready.

To draw the slice of the next group place the protractor at the end of the previous group and mark the next central angle.

Draw the radius that passes through this mark to obtain the second slice. Repeat this process until every slice is drawn.

Make sure that the sum of the central angles is equal to 360^(∘). 144^(∘) + 108^(∘) + 108^(∘) = 360^(∘) ✓ Be aware that the central angles are not typically shown on the final diagram.

Add the Details to the Graph

Finally, color and label each slice of the graph.

Side labels and relative frequencies written as percentages might also be added in this step.

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