Dos and Don’ts of Data Visualisation
Whether on purpose or not, a statistician can mislead an audience with a chart. This article explains some chart design principles and common mistakes novice data analysts make. Think about the statistical charts you have seen on billboards, in the news, and in research studies. Using these principles as a guide, would you classify any of those charts as misleading? Be sure to take note of the suggestions for successful dashboards.
Choose your chart
Bar chart: do use the full axis and avoid distortion
For bar charts, the numerical axis (often the y-axis) must start at zero.
Use the full axis for bar charts. Our vision is very sensitive to the area of bars and we draw inaccurate conclusions when those bars are truncated.
If you need to show data details that are not visible when using the full axis, then the original chart with full axis can be accompanied with a 'zoomed-in chart', a so called 'panel chart' in Excel. See example below:
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Making these charts interactive will solve many of the issues stated above. For example, the user would be able to mouse-over a column and get the exact value, filtering out some categories or sorting the columns according to their values for easier comparison.