Common Mistakes

We have curated a list of common mistakes, but recommend you walk through the 3 steps to designing your charts. Being aware of these steps will enable you to successfully avoid the below mistakes from a place of informed decision making.

Design your chart in 3 steps:
1) Identify the Purpose of your chart.
2) Choose the appropriate chart.
3) Apply the SHARC (Scale, Hierarchy, Axis,Readability, and Color) Framework.

Scale

Use consistent scale divisions to accurately represent the range in values of the data presented.

Bar Chart

Here, scales across y-axis is not consistent. From the difference of 10 unit, it changed to difference of 20. Visualizing trends could be misleading in such cases. However, scale breaks could be used to represent extremely high/low data points.

Pie Chart

The sum of slices is not adding up to 100%. This is one of the common mistakes when it comes to representing data on a pie chart. Pie chart is better for representing part to whole data.

Small Multiples

Keeping the scales consistent is even more important when it comes to small multiples. Standardizing the scales helps in comparison otherwise it could give wrong inference.

Histogram

Histogram shows the distribution of data. In this case, 60-70 and 70-80 should have been shown empty to show 0 value in those two bins. This could have given a clear picture about the frequency distribution.

Bar Chart

Here, the Y axis is not consistent. It started with a 10 unit difference, then changed to a 20 unit difference. Visualizing trends in this way can be misleading.

Pie Chart

The sum of slices does not add up to 100%. Pie charts are intended to represent parts to a whole data.

Small Multiples

The scales in this small multiples chart are different. Standardizing the scales allows for easy navigation; and thus, comparison across the same slices of the dataset across different categories.

Histogram

Histogram shows the distribution of data. In this case, 60-70 and 70-80 should have shown 0 value in those two bins instead of not including them. This would have given an accurate picture of the frequency distribution.

Hierarchy

Hierarchy enables us to give a clear and precise visual path to the overall story. Name your data story accurately and concisely through the title and organize a visual path of details to support it.

Bar Chart

In this visualization, all the elements inside the visualization carry similar weight. There is no clear path for the viewer.

Pie Chart

Depending on the purpose of chart, we can use color to bring contrast to the slices of pie chart. However, in this case one slice is taking all the attention.

Boxplot

Lengthy title could sometime take unwanted attention and distract the viewer from the main story. In this case, the title is grabbing a lot of attention.

Histogram

Sometimes, inappropriate use of color could lead to unwarranted attention. However, the decision to use contrasting color could depend on the purpose of creating that chart.

Bar Chart

In this visualization, all the elements inside the visualization carry similar weight. There is no clear path for the viewer. Differences in font size and boldness, minimal and impactful use of color, all help the viewer know where to start.

Pie Chart

Color can be used to help the viewer know where to focus in the chart or where to began reading. In this case, one slice is taking all the attention, which may lead to an unwanted detour in reading the chart. Sometimes, when you want to focus on a single number or percentage, it can be effective.

Boxplot

Lengthy titles, such as this, can sometimes take attention away from the main story. If the viewer is having to read it over and over to understand it, it's not effective.

Histogram

Making sure all elements are in alignment is part of directing viewers from most important to supporting details. In this case, an off-centered title is distracting and can cause viewers to return to it repeatedly and unnecessarily.

Axis

Axis plays an important part in visualization. Sometimes, we need to follow the "zero rule"; other times, we're required to modify the axis to suit our purpose. It can also vary depending on the choice of visualization.

Bar Chart

In bar chart, if we truncate the y-axis, it could mislead the viewers. In such cases, even the small difference across categories could look like a big difference. However, 'zero rule' may not necessarily apply to other chart types including line chart.

Pie Chart

Although the axis is not clearly pronounced in pie chart, it is generally recommended to start the slices from either 0 or 90 degrees, in order to make a pie chart easy to read.

Small Multiple

It is extremely important to keep the axes same in small multiple. Not keeping it same would hinder the inference capabilities of viewers and would most likely result in wrong insights. In this case, both should have started from 30 or 40.

Back to back

Here, it is difficult to compare across categories in back to back chart. It could have become easier to gather insights if the categories on the y-axis were arranged in either ascending or descending order.

Bar Chart

In bar chart, if we truncate the Y axis, it could mislead the viewers. In such cases, even the small difference across categories can look like a big difference. However, "zero rule" may not necessarily apply to other chart types including the line chart.

Pie Chart

Although the axis is not clearly pronounced in pie chart, it is generally recommended to start the slices from either 0 or 90 degrees, in order to make a pie chart easy to read.

Small Multiples

It is important to keep axes the same across small multiples. Not keeping it same would hinder the inference capabilities of viewers and would most likely result in wrong insights. In this case, both should have started from 30 or 40.

Back to Back

In this case, it is difficult to compare across categories. It would have been easier to gather insights if the categories on the Y axis were arranged in either ascending or descending order.

Readability

Always clear the visual path of any clutter and use easy to read fonts and graphic elements

Bar Chart

Making the grid more pronounced could impact the readability of overall chart. This is something Edward Tufte, called as 'chart junk'.

Pie Chart

Often it is fascinating to see the charts in 3D but most of the time, it's difficult to read 3D charts. It creates confusion because of depth of field.

Back to back

Adding icons and graphics could create additional clutter in the visualization. However, graphics have their own benefits. Studies have shown its impact on improved chart memorability.

Histogram

One should always be careful while using "attractive" typefaces. Some typefaces could seriously hamper the readability. Also, make sure define a minimum font size for accessibility reasons.

Bar Chart

Having the grid so pronounced distracts the viewer from reading the data.

Pie Chart

It may seem like we are increasing understanding by presenting charts in 3D, but it's one more unnecessary factor to try and understand for the viewer.

Back to back

Adding icons and graphics can create clutter in the visualization. However, there are times when purposeful use of graphics can increase the impact of the information presented.

Histogram

One should always be careful while using "attractive" typefaces. Some typefaces can hamper readability. Also, make sure define a minimum font size for accessibility reasons.

Color

Employ sparingly and intentionally and make accessible.

Line Chart

Using more that 3-4 different color is generally not recommended. This could become cognitive load for the users.

Pie Chart

While using color in pie chart, one needs to be extra careful. Here, the contrast between the slices are not enough to distinguish them clearly.

Small Multiple

Here, it is extremely difficult to read the chart. It is recommended to have enough foreground to background contrast to ensure the legibility. Further reading: W3 accessibility guidelines.

Histogram

One should not use color just for the sake of adding it. It should serve some purpose. For example, in the about visualization, we're not getting any additional information by using color.

Line Chart

Using more than 3-4 different colors can overwhelm the viewer as she tries to navigate what each color means and apply it to navigating the graph.

Pie Chart

Using enough contrast in color choices to meet accessibility standards (non-text contrast ratio of at least 3:1 is suggested for accessibility by WCAG 2.1). In this case, there is not enough contrast. Check out our References & Resources > Accessibility & Color to learn more.

Small Multiple

In this example, it is difficult to read the chart because there is not enough contrast between the foreground and background. Further reading: W3 accessibility guidelines in our References & Resources > Accessibility & Color.

Histogram

There's no need to use a lot of colors in every chart. It should serve a purpose. Decide if the bars can all be one color. And if it's important they are different colors, check out our References & Resources > Accessibility & Color to learn more about the type of color scheme to use and how to ensure it is accessible.