Reports, presentations, and web pages frequently use tables and graphs. Authors can present data using graphs in a way that is easy for their audience to understand. Data tables let the audience see the entire data set at a glance. Accessibility opportunities and challenges exist for both graphs and tables. In this article, we discuss both topics.
Accessibility benefits of using graphs
Graphs are visual representations of data. You can use graphs to complement data tables and narrative descriptions to represent information in reports.
Using graphs can help you meet the needs of people with cognitive and learning disorders. Even though they represent about 13% of the US population, people often overlook them in discussions of digital accessibility.
Many people need to put more words on their slides in PowerPoint presentations. A graph that illustrates the point you are trying to make might replace an entire paragraph.
Color
Color is a great way to visually separate or group data in a graph. However, it causes a challenge for people with multiple kinds of disabilities. A person who is colorblind or a person with low vision might not be able to see the difference between the two colors used. This doesn’t mean you can’t use color. It means you must use sufficient color contrast and cannot use color as the only means of expressing information.
Example 1: Pie Chart
Pie charts are a common way to visually show how a larger group breaks down into smaller groups. For example, the accessibility coordinator as a business could use a pie chart to show the results of a survey of customers on how many of them have a disability.
Pie charts typically use a different color for each subgroup of the data. In this example, three colors represent three subgroups. A legend associates each piece with a color. This pie chart is not accessible because it uses only color to convey information.
The accessible version of this example is different in two key ways. The parts of the pie are pulled apart so that the audience can see the size of each piece without needing color.
Additionally, the labels are directly on the pieces.
Like all visuals, graphs must have alternative text. For a simple pie chart like this, write alt text that identifies the type of graph and approximately how much of the total each piece represents.
Example: Inaccessible pie chart
Example 2: Line Graph
Authors and presenters can use line graphs to show how data changes over time. In example 2, three lines represent how three different types of data changed over time. For example, the accessibility coordinator at a school might use a line graph like this to show student test scores throughout the school year.
This example is not accessible for someone who is color blind or has low vision. It relies on color and the lines cross over each other multiple times.
In an accessible version of this line graph, the lines have different shapes at each data point. This way, a person who is colorblind or has low vision can tell the three lines apart.
Writing alternative text for this graph is more difficult than the pie chart. One strategy is to write a general description with instructions to refer to a data table for details.
Example: Inaccessible line graph
Example: Accessible line graph
Accessibility benefits of using tables
One of the main challenges is that data tables can be difficult to read and understand. This is especially true for tables with a large number of columns and rows. Users may have trouble finding the information they need or understanding the relationships between different pieces of data. To address this challenge, it is important to design tables that are easy to read and understand. This can be done by using clear headings, consistent formatting, and appropriate colors and fonts.
Making accessible tables in Word and PowerPoint
The accessibility principles of Word and PowerPoint are the same. This section describes what you should and should not do when creating a table.
Tables require alternative text like all visuals. The alternative text for a table should be a simple statement describing the purpose of the table.
Sighted users can glance at the header row to see what column the cell they are looking at is in. Screen reader users cannot quickly do this. Always make sure to select the option “repeat header rows.” Selecting this option helps orient a screen reader user as they tab through a table. When the user tabs to a cell, the screen reader will read both the column's name and the specific cell's contents.
There are a few things you cannot do unless you have advanced software such as CommonLook. Do not merge or split cells. This interferes with the principal just described. Similarly, do not leave cells blank. If you don’t have any relevant information to put in a cell, you can enter something like “N/A.”
Conclusion
Both graphs and tables have accessibility benefits and challenges.
Graphs allow you to visually represent data, benefiting people with cognitive and learning disabilities. However, you must include alternative text and be careful about your use of color. It is important to note that you should only use graphs when necessary when presenting data and avoid using them for decorative purposes.
Tables can provide information to screen reader users when writing alternative text for a graph is impractical. When creating a table, it’s important to include alternative text and select “repeat header rows.” additionally, avoid merged, split, and empty cells. It is important to note that you should only use tables when necessary in organizing data and avoid using them for decorative purposes.
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