How Do Tech Writers Use Visual Elements to Depict Data?

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ChartTechnical communicators have many reasons for incorporating visual data (specifically tables, charts, and graphs) into their work: they make text easier to understand, they often save on production costs, and translation to other languages is usually easier. So, the problem for many writers isn’t if to include charts, graphs, etc.; the problem may be when to use each type.

The process for incorporating these elements is simple:

  1. Know your message
  2. Compile the data
  3. Create the chart/graph/table
  4. Format the visual element to meet style and aesthetic guidelines

The practice of incorporating these elements proves to be a little more tricky. In order to use the correct visual representation of numerical data, writers must understand each available option, its purpose, and its distinctions among other options.

Technical communicators need to understand the basic reasons for using these visual tools:

  • To compare
  • To show the distribution
  • To explain parts of the whole
  • To show rend over time
  • To show deviations
  • To explain a relationship

Defining Each Chart Type

Vertical bar charts are best for comparing mean or percentages between 2 to 7 different groups. The x-axis should be based on a scale that has mutually exclusive categories (unlike a histogram where the x-axis units depict segments of the same unit).

Horizontal bar charts are used when comparing the mean or percentages of 8 or more different groups. As with vertical bar charts, horizontal bar charts should only be used when comparing categories that are mutually exclusive.

Histograms are graphical displays of data using bars of different heights. They are similar to bar charts, but histograms group numbers into ranges to illustrate sample distributions within discrete intervals. Histograms are great to show results of continuous data (rather than categorical data).

Scatter plots are used to depict how different objects settle around a mean (also called a trend line) based on 2 to 3 different dimensions. They allow for quick and easy comparisons between competing variables. Readers can quickly reference the difference between two objects or their relation to the average.

Line charts use points connected by lines to show how something changes in value. Line charts illustrate trends over time.

Pie charts are circular charts divided into sectors, with each sector showing the relative size of each value. They are best used to illustrate a sample breakdown in a single dimension. In other words, it is best to use pie charts when you want to show differences within groups based on one variable. It’s important to remember that pie charts should only be used with a group of categories that combine to make up a whole.

The table below summarizes the purposes of each chart/graph type:

  Bar Scatter Pie Table Line Histogram
Comparison X X X X X
Distribution X X X
Parts to Whole X X X
Trends X X X X
Deviations X X X X
Relationships X X X






Obviously, you can use more than one chart type to graphically relay information to your audience. So how do you know which one is the best to use? Use common sense. Use what you know about the audience, their level of expertise/experience with the information you’ve provided, or rely on precedents to determine which one will best serve your purpose. Keep it simple, well-labeled, and well-organized. Use colors with high contrast, and make the boundaries of the chart clear. Finally, include text references to your chart that include the title and location, and include a brief description of the chart in the caption or label.