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Microsoft Excel 2003/2004

Guidelines for Charting

The ability to create effective charts, whether for oral presentations or printed text, is an important skill for anyone involved with projecting numeric information. Research has shown that visual depictions of data communicate faster than words or lists of numbers. Knowledge of effective charting methods allows you to present numerical information in a visually appealing way. Essentially, a chart's effectiveness depends on its ability to generate for the viewer an immediate sense of orientation and access to information.

return to topGeneral Hints

Generally, effective charts use the simple techniques of good design. Any reference material discussing page layout will assist you in this area. Some design techniques are especially important, as they relate directly to charting. These techniques include the following:

Choosing the correct chart format
Chart formats are designed to portray certain types of information; therefore, choose the correct chart format for your information.

Maintaining simplicity
Clarifying information is the main goal of creating a chart, so complicated charts only serve to make your information less clear.

Maintaining consistency
When creating several charts, use a design grid. This grid will help you maintain a consistent chart format, eliminating distractions for your audience.

Using labels
Effective use of labels that are created using legible typefaces will assist your audience in understanding a chart's information.

Each of these design factors is important, but the choice of chart format comes first. For this reason, the following sections discuss the design considerations for three of the most common chart formats.

return to topPie Charts

Pie charts are best used to compare parts of a whole; in other words, they help divide a group into components. Some factors to keep in mind when creating pie charts include the following: 

Pie chart
Source: UWEC Campus Profile, 2001

Limiting the number of slices
Keep the number of slices to a minimum by combining smaller categories into one.  Too many slices will hinder interpretation by making your pie chart appear complicated and cramped; it will also create difficulties for labeling.

Using labels for slices
Try to place labels within slices whenever possible; this will help you create pie charts that are both clear and readable.

Focusing attention
If necessary, draw your audience's attention to the particular slices you are discussing, perhaps by "exploding" it to make it appear separate from the pie or by selecting a dominant color or pattern. For more information on enhancing pie chart effects, refer to Using Pie Chart Options.

Enhancing the chart
Consider enhancing the appearance of the pie chart, perhaps by adding perspective.  Keep in mind, however, that three-dimensional pies can sometimes make certain slices appear larger than they really are; thus, your pie chart may be misleading.

return to topBar Graphs

Bar graphs work best to emphasize the contrast between quantities. Two types of bar graphs can be used: vertical and horizontal. Vertical bar graphs work well for comparing quantities at different times, while horizontal bar graphs compare different quantities when time is not an important consideration. For example, a graph showing student enrollment by year would probably work best in the vertical format, while a graph showing current participation in faculty organizations would be most effective in the horizontal format. Some design considerations to keep in mind when creating either type of bar graph include the following: 

Bar graph
Source: UWEC Campus Profile, 2001

Column Graph example
Source
: UWEC Campus Profile, 2001

Limiting the scale
Make sure your bar graph is kept within a reasonable scale; in other words, try to avoid showing three quantities of similar size and one quantity that is drastically larger or smaller.

Enhancing the graph
Consider adding perspective or a drop shadow to your chart for visual appeal, but again, be aware that (as with pie charts) the third dimension can confuse or even mislead the audience. Numerical values placed above or within the bars themselves may help solve this problem. For more information, refer to Formatting Your Chart.

return to topLine Graphs

Line graphs best indicate the relationship of one variable to another, and they can be created using either straight or curved lines. Which type of line graph you use depends on the type of information you wish to convey: straight-line graphs show specific observation points, while curved-line graphs show general trends. Some design considerations to keep in mind when creating either type of line graph include the following: 


Line graph
Source: UWEC Institutional Planning, 1999-2003

Line Graph
Source: UWEC Institutional Planning, 1999-2003

Using contrast
Make sure to use lines with sufficient contrast; in other words, create a line that is bold enough to clearly appear to your audience but thin enough to still convey specific information.

Limiting multiple lines
When using multiple lines to compare trends, keep the number of lines to three or less. Comparing more than three trends on the same line graph can create confusion for your audience, especially if your graph is not in color.

return to topSummary

Adhering to the guidelines in this document will help you create charts and graphs that present information clearly. Of course, the three chart formats discussed here are not the only ways to convey numerical data; other formats can effectively portray information as well. The following table provides a quick guide to most of your choices:

Chart Format Description
Pie Compares parts of a whole
Bar Shows contrast between quantities
Line Indicates the relationship of one variable to another
Area Indicates the volume relationship of one variable to another
Scatter Plot Correlates two factors by marking the points where particular events occurred

Each chart format has its own design considerations, but you have plenty of room for experimentation. You can use your computer software to try new techniques. As long as you choose the correct format and keep in mind the general concepts of simplicity, consistency, and labeling, you will be well on your way toward creating an effective chart that is understandable and effective.

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