Pie Charts

Understanding Pie Charts

• A pie chart is a type of graph used to represent categorical data.
• It’s a circular graph, where the whole circle represents the total or whole of the data.
• Each sector or ‘slice’ of the pie represents a category within your data.
• The size of each sector is proportional to the frequency of the category it represents.

Constructing Pie Charts

• To draw a pie chart, you first need to work out the angle for each sector.
• The angle can be calculated with the formula: (frequency of the category / total frequency) x 360.
• Make sure that the sum of all your angles is 360 degrees.
• Use a protractor to measure the angles and draw your sectors accurately.

Reading Pie Charts

• The bigger the sector, the higher the frequency for that category.
• Remember, the visual size of the sectors can sometimes be deceptive, always refer to the exact figures if provided.
• Pie charts do not show the total frequency or amount of data.
• They are typically used to compare parts of a whole and not to compare data between different pie charts.

Limitations of Pie Charts

• Pie charts become ineffective if there are too many categories as the sectors become too small to compare easily.
• They are not suitable for representing small differences in data.
• They can be misleading if the sectors are not drawn accurately or if 3D effects are used.

Advantages of Pie Charts

• Pie charts provide a visual representation, making it easier to understand the proportions of categories in a data set.
• They are a quick and easy way to get a general overview of the relative distribution of data.