Pie Charts

• Pie charts are a type of graph presented as a circle, split into segments (“slices”) to represent various categories of data.
• Each slice of pie chart corresponds to a particular category, and the size of each slice is proportional to the quantity it represents.
• The entire pie represents the total data set, while each “slice” represents a portion of the whole.
• The size of the slice (angle or area) in a pie chart is directly proportional to the frequency of the category that it represents.
• To find the angle/degree of each slice, multiple the relative frequency of the category by 360° (total degrees in a circle).
• When creating a Pie chart, add up all your data to get a total, then divide each category by the total and multiply by 360° to find the angle for each slice.
• Pie charts are used for displaying relative frequencies for different categories.
• Be cautious when comparing data from two different pie charts, as the visual representation could distort the magnitude differences if not properly done.
• It’s important to label each slice with the related category and its percentage or value.
• Pie charts are best used with discrete or nominal data categories which do not overlap.
• Limitations of pie charts include the inability to accurately compare sections that are close in size and difficulties interpreting charts with many sections.
• Lack of precision in reading a pie chart is a common criticism, hence they are not typically used for precise comparisons as it can be difficult to judge segments of similar size.

Remember: Practice drawing pie charts regularly to get accustomed to calculating the degrees and representing relative frequencies accurately.