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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?
To provide 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. Place the sum total in the last cell
(b).
- In column (c), compute the fraction of the total
that 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.
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Case Study
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