You’ve been tasked with making a presentation on some important business figures – financial updates, results of marketing efforts or other key data – and rather than create text-heavy slides with lists of numbers, you know that putting the data into a graphical format will be more interesting and visually appealing to your audience. When used properly, charts and graphs are a very effective way to communicate data. However, simple missteps in design can muddle your data, weaken your message and confuse your audience. Avoid common mistakes by following these best practices to ensure that your message is heard loud – and clear!
You may be surprised to hear that the pie chart – one of the most commonly used statistical graphics in business, marketing and media – is considered “data visualization’s greatest villain” according to experts in the field. So how did it earn its bad reputation? It turns out that pie charts are actually pretty hard to read. Our brains aren’t the best at interpreting the size of each slice of pie relative to one another, and when there are too many slices, or slices that are too close in size, we really struggle to grasp what it is we’re being shown.
That isn’t to say that you should never use a pie chart again, but if you do, there are several rules to follow:
- The fewer slices, the better: Too many slices makes a chart difficult to read. Try to limit yourself to five or fewer sections, ideally with data points that are significantly different enough to make the slices discernably different in size.
- The largest slice should start at the top of the chart, then work your way around the circle in increasingly smaller slices.
- Avoid comparing pie charts to one another: If one pie chart is difficult to read, interpreting multiple pie charts is even harder. The three pie charts below depict changes over a period of time. Some of the slices noticeably grow or shrink, but determining if others change (and if so, by how much?) is much harder. Taking that same data and putting it into a bar graph allows us to see these changes much more precisely and in a format that is easier for our brains to interpret.
- Don’t use 3D pie charts: The tilted angle at which these kinds of charts are displayed can make sections in the foreground appear deceptively larger than those in the background. In the example below, “A,” “B” and “D” each represent 10 percent of the pie chart, but they don’t appear to be the same size.
Another common presentation selection, the bar graph is considered slightly more acceptable than its problematic cousin, the pie chart. However, improper design of a bar graph can reduce your data’s readability and clarity. Follow these rules to ensure your graphs convey your message accurately and effectively:
- Easy readability: Don’t make your viewers tilt their heads to read labels on an angle; switch the information on the axis so that your longest labels can be read horizontally.
- Rank data points by size: It’s difficult to understand the comparative size of each bar when they’re not in order. The exception to this is to when using multiple graphs to depict changes over time.
- Avoid 3D charts: Just like with pie charts, 3D makes your data difficult to read. It also distracts from the information you’re trying to present.
- Leave out the Y-axis lines: This isn’t as egregious a mistake as the others are, but data visualization experts recommend omitting the background lines in your bar graph, as they only add clutter.
Taking just a few extra steps to ensure you’re following the rules of data visualization will help you create charts and graphs that are trustworthy, unambiguous and persuasive. In turn, they will convey your data in a much more powerful way. Unsure of where to start? Reach out to AOE for help getting your message across effectively and accurately.