Data Visualization in Environmental Public Health: From Data to Insight
Using Misleading Axes, Scale, or Categories
How to Make It Better Use a wider y-axis range so the bar lengths accurately represent the differences between months. • Use evenly spaced intervals that cover the full range from zero to the highest value. • Add data labels if the audience needs to identify the exact monthly totals. • Include a brief annotation if a small difference has practical importance. • If the purpose is to highlight subtle month-to-month changes, consider using a line chart or dot plot and clearly indicate that the axis does not begin at zero.
What’s Wrong with This Visual? The y-axis begins at 500 and ends at 510, creating a narrow scale that exaggerates small differences in the monthly number of completed inspections. • The y-axis does not begin at zero, even though bar charts communicate differences through bar length. • January had only nine more completed inspections than December, but the bars make the difference appear much larger. • The truncated axis may lead viewers to conclude that inspection activity varied substantially across the year. • The chart does not provide context to explain whether these small monthly differences are meaningful.
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