CHOOSING VISUAL AIDS
Deciding which type of visual aid to use is sometimes difficult. The best way to choose is to decide what your readers need. If your readers need more scientific or “more objective” data, use tables and line graphs. Tables can classify large amounts of data so that relationships can be easily pointed. out. Pie and bar graphs have more visual impact or drama. If you look back at the bar graph shown in Chapter 1 you will see that it presents information dramatically. The towering columns clearly reinforce the notions of “critically important” and “important” as opposed to the short column of “no importance.” The difficulties – and ch of deciding what visual aid to use can be seen in the following figures. All four figures, constructed using Microsoft are attempts to convey the material presented in the table in Figure 7.14. The table compares the costs of manufacturing WORM disks (a type of computer floppy disk) from 1980 to 1987 in four areas: testing, thin films, assembly, and coating. The four types of figures consist of a divided bar graph, one bar for each year ( two bar graphs, one for each year a bar graph showing bars for each component(Figure and two pie charts, one for each year Notice the effects. The two bar graphs emphasize changes in the relationship between items in each year. It is easy to see the relationships between.
Components of Cost of Disks
A Table Compares the Data
A Divided Bar Graph Compares the Data
testing and thin films for each year, but the two vertical axes (“Dollars”) are based on different scales, so comparison is difficult. The two pie charts (Figure 7.18) take time to figure out because they are separated from each other. Notice that they do show that the total cost has change~’and that the relative percentages of thin films and testing have changed .
The divided bar graph shows the. relationships between the components and the total cost. This visual shows essentially the same information as the two pie charts. Because of the closeness of the two columns, however, the comparative relationships are easier to grasp. The bar graph with two columns for each component contrasts dollars, not percentages, clearly illustrating all the reasons why 1987 is cheaper overall than 1980. If readers need to understand dollar breakdowns, would serve their needs better. If readers need percentage breakdowns, the divided
bar graphs or the pie charts would help them more. However, jf readers need precise figures and if they can’ work easily with relationships, the table would be a good choice .
Two Bar Graphs Compare the Dala
Multiple Bar Graph Compares the Data
Two Pie Charts Compare the Data
Three Principles for Manipulating Graphs
Ian in his book Using Charts and Graphs, illustrates three ways that you can affect the perception’ of graphic data. Your goal. is to present the graph so that it reports the data honestly
- Changing the width of the units on the y-axis alters the viewer’s’ emotional perception of the data. The following graphs plot exactly
the same data (Figure 7.19).
Three Graphs Plot the Same Data
Solution: Reprinted by permission of R. R. Bowker
- The nearer a highlighted feature appears, the more impact it has
on one’s consciousness. The following pies report the same data.
Notice that the wedge on the left appears largest, but the wedge on
the righfis forced into the viewer’s consciousness. The middle wedge
appearsunimportant because it is far away (Figure 7.20).
Three Pie Charts Plot the Same Data
SOli Tee: Reprinted by permission of R. R. Bowker
- A darker element seems more important to the viewer (Figure 7.21).
Three Bar Graphs Plot the Same Data
Source: Reprinted by permission of R. R. Bowker.