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Book Contents

Ch. 5
Designing and Evaluating DSS User Interfaces

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Comments on Design Elements

Graphics, including charts, enable the presentation of information in a way that can clearly show the meaning of data and permits users to visualize relationships. The importance of using charts and graphs in communicating numeric data has been recognized for many years. Since the mid-1970s, computer graphics have been used to aid in management decision making. Graphics help managers "visualize" data, relationships, and variances. Common types of computer graphs and charts include time-series charts, bar and pie charts, scatter diagrams, maps, hierarchy charts, and flow charts. Managers, business analysts, and corporate staff use computer generated graphics in reports, presentations, performance tracking, scheduling, control, planning, modeling, and design. It is important to use graphics in the DSS user interface, especially in data displays. An end user tool like Excel has a wizard that helps create charts. Some of the charts available in Excel are shown in Figure 5.5.

Figure 5.5 Some Excel Chart types.

Letís summarize some guidelines for graphical displays. Communicate only one major message on each chart or screen. Use an action heading in appropriate sized fonts for screen and chart headings. A line chart is appropriate for displaying time-related information, but analysts need to be careful to use appropriate labels and to avoid adding dissimilar quantities. Bar charts are more appropriate for comparing individual data values. Pie charts help show how the whole breaks down into component parts. You should limit the number of components or pieces in a pie chart to five or fewer.

Color is often recommended as a means of enhancing a user-interface design. Appropriate use of color can enhance the aesthetics of an interface for most people. Color can call attention to extreme or exceptional data values, help users differentiate among items on a chart, and convey information quickly. For example, research indicates blue creates a sense of trust; green means "go" or "all clear;" red indicates danger. In general, the following guidelines related to the use of color are appropriate for DSS:

  1. Do not allow color to be the only way your system conveys any information. Augment the use of color with other cues that can be used by people who cannot see the color difference. Include numerical values in addition to color codes, provide cross-hatching on top of color, or make sure that the colors you choose are perceived as substantially lighter or darker than each other.
  2. Where your computer hardware and software permit, allow the user to customize an application's use of color. Changing colors can compensate for some peopleís color vision deficiencies. In some systems, colors that cover an area, such as a region on a map, can be replaced by monochrome patterns such as dots, stripes, and cross-hatching.
  3. Use light pastel colors in screen designs. They create fewer annoying reflections than do dark colors. This is especially true in an office environment with fluorescent lights. As a result, try to use light colors to cover large areas of the screen. Reserve darker colors for smaller "spot" usage.

Human-computer interaction is an important design issue. An interaction issue, unique to DSS and often not adequately considered, is the type and amount of guidance, called decisional guidance, that a DSS provides its users in the decision-making process (cf., Silver, 1991).

Decisional guidance provided by a system can be unintended or inadvertent. For example, users tend to select the first or last items from menus. Putting a frequently used capability in the middle of a menu may not be planned. Decisional guidance can also be planned and deliberate. Designers can intentionally build guidance mechanisms into a system after determining that a particular decision approach or process is better than what many users would come upon by chance. This type of planned, process guidance is distinct from the typical on-line help facility, which focuses on guidance in the mechanical aspects of operating the system. On-line help assumes that the user has already decided what to do, but does not know how to do it. Process guidance assume the user need direction in using the system.

Some DSS give the developer more of an opportunity to provide decisional guidance than do others. A DSS that does not provide for many discretionary user judgments during its use cannot benefit greatly from such a guidance facility. A DSS that lets users choose among several decision methods, several alternative models, several ways to cross tabulate a set of data, several forecasting techniques, or even alternative sequences of activities does provide an opportunity to provide decisional guidance.

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