Numerical information can be displayed in a variety of ways, each of which is suited for displaying a particular type or quantity of data. Many options are available for presenting data, especially with the advent of word processors, spreadsheets, and graphics software programs for creating tables and graphs.
In order to communicate information decisions effectively to users, designers need to understand the tasks in which readers engage when they look at displays. Because the user's tasks require certain sensory, perceptual and cognitive operations, one has to consider what type of information the user is trying to ascertain in reading the graph. For example, a well-designed line graph makes it easier to discern the slopes of lines, whereas, if the user's goal is to determine actual values at certain points, differentiating slopes is of little value.
There are various factors in making a decision about how to present data. The first factor concerns the amount of data being presented. When presenting a small amount of data, authors should weigh the communicative benefits of tabular or graphical presentation against the reader's cognitive costs. Generally, in this case, tabular presentation is preferred. However, with a large amount of data, the reader's use of the data, especially the degree of precision the reader is likely to need, becomes important. When relations are more important than precise values, the data is probably best displayed in a graph.
Finally, one must then choose the type of graph to present the information. This decision depends on both the characteristics of the readers and of independent and dependent variables. Generally, common graphs with which all readers are likely to have experience are used: line graphs, bar graphs, pie charts, and scatter plots. The choice of graph type depends on the readers' informational needs. Either a line graph or a bar graph is used if readers need to determine relative or absolute amounts. A line graph is used, for example, when a user needs to determine the rate of increase of a dependent (criterion) variable as a function of change in an independent (predictor) variable. A bar graph is used when a user needs to determine the difference between the means of the dependent variable across different levels of the independent variable. A pie chart is commonly used when a user needs to determine primarily proportions but not absolute amounts. However, the type of information each of these graph types can convey is limited. For example, a pie chart can only display one aspect of an underlying data set. If the underlying data set consists of two aspects, company profits as well as company losses, two pie charts are required. One for the company profits and one for the company losses.
Thus, given the above background, what is needed in the art are improved systems and methods for displaying data.