Designing for accessibility

1. Designing for accessibility

To this point, we've looked at several ways to improve dashboard design. Now we're going to focus on making them accessible to more people.

2. Color vision deficiency (CVD)

Color vision deficiency affects approximately 8% of men and 0.5% of women. The most common form of this is caused by a lack of adequate cones in the eyes to detect certain colors, and this is split into whether you have insufficient cones or a total lack thereof.

3. Color vision deficiency (CVD)

This chart shows the breakdown of how likely a person is to have each.

4. CVD in action

Here is a screenshot from SQL Server Integration Services 2008 which shows the problem with using color as a signal. If you have full range of color vision, you can easily see what succeeded and what failed. Here is what the flow would look like with tritanopia. We can still easily distinguish results. But with protanopia or deuteranopia, it becomes much harder to differentiate failure from success, and with certain hues of greens and reds, it would be impossible to separate the two.

5. Tips for better color usage

The best advice for color usage is, use less of it. This reduces color overlap and lets us use color as a pre-attentive attribute. If you do need to use color, choose a color palette which is CVD-safe. Power BI offers some of these. Also, include indicators other than color, such as labels. Finally, use tools like the Coblis color blindness simulator. This tool can show that there is a lot of color overlap on our treemap for people with protanopia, but the labels can help us differentiate values.

6. Font Sizes

Power BI defaults to small font sizes. The DataCamp theme you've used so far has default font sizes of 15 points, which is a good minimum. This makes it easier for people to see, especially on smaller form factors like mobile phones.

7. High Contrast Mode

Windows offers a native high contrast mode which Power BI supports. High contrast mode removes colors from images, making it all the more important not to rely on color as your primary signal.

8. Increasing contrast

For users not in high contrast mode, keep the contrast ratio in mind. This is the difference in perceived brightness between two colors, whether font, image, or background. Web standards recommend a contrast ratio of at least 4.5:1 for normal text and 3:1 for larger text. Background images and background colors other than black or white typically lead to lower contrast ratios. Use contrast checking tools to ensure you have sufficient contrast in your reports.

9. Screen readers

Power BI supports screen readers, but with some caveats. Because reports are so visual-heavy, Power BI offers a shortcut to show the data as a table, making it easy for screen readers to work. The Alt Text formatting option describes a visual. This only shows up when using a screen reader and can read static text or the value of a field. Power BI is not perfect for accessibility: you cannot drill into or cross-filter elements using the keyboard and readers will not work on everything.

10. Smart narratives

Smart narratives are not a traditional accessibility option but can be a unique way of describing the results of a visual. The visual automatically populates with interesting text, but you can introduce your own using its Q&A-like functionality.

11. Our audience

Our target audience this time is still a research organization looking to understand inflation trends, but now we have people who may have accessibility requirements. Because of this, we will tailor the reports to focus on accessibility.

12. Let's practice!

Now let's get out there and improve those reports!

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