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Pie Chart
What is it?
A pie chart is a tool that helps you visualize the relative
importance of several categories of a variable.
Who uses it?
The team, the manager.
Why use it?
If you want a rapid, graphical overview of data you
have collected, such as information about different
types of users, types of treatments, types of methods,
etc.
When to use it?
When you have collected some data (for example, a counting
of events or a distribution of values) and you want to
graphically depict the data.
How to use it:
With the help of a table, transform your data into percentages
of the total.
- Select the number of categories for organizing the data.
| Categories |
(a) |
(c) |
(d) |
| | Number of
Events | Fraction of
Total
Categories
(a ÷ b) = c | Percentages
d = (c X 100) |
| Data 1 | 24 | 0.333 | 33% |
| Data 2 | 28 | 0.388 | 39% |
| Data 3 | 12 | 0.166 | 17% |
| Data 4 | 8 | 0.111 | 11% |
| Total
(b) | 72 | | 100% |
- In column (a), fill in the number of events or
data for each category. Put the sum total in the bottom cell
(b).
- In column (c), compute the fraction of total each category represents by dividing (a) by (b). The results in (c) will always be decimals.
- Multiply each number in column (c) by 100 to obtain a percentage and round to the nearest whole percent. Enter the percentages in column
(d).
- Check your calculations by totaling the percentages listed in column (d). The sum of percentages should equal 100.
- Draw the pie chart.
- Draw a circle.
- Represent the values of the different categories on the circle in
percentages. If you are not using a computer to create the pie chart, draw guides to help you (divide the circle into four or eight equal
parts).
- Title your graph and indicate in the legend the period of time of the survey, as well as the location.
Example:
Here is an example of a pie chart being used to describe a problem.
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Case Study
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