Data Visualization in Environmental Public Health: From Data to Insight
Figure 1 Bar Chart Example: Grade Distribution of Inspections
Common Visualization Types Comparing Groups and Categories
Many EPH questions involve comparison. Programs might need to understand how inspection outcomes differ across districts, whether complaint volume varies by facility type, or how workloads are distributed among staff. When the goal is comparison, bar charts are often the most appropriate choice. Bar charts make differences in values between categories easy to identify and interpret, even when comparing multiple groups. Common examples include: • Number of inspections conducted by district • Complaints by facility type • Violations by category • Permits issued by program area Stacked bar charts can be useful when showing the composition of a larger category. For example, a stacked bar chart can display critical, major, and minor violations within each inspection district.
Pie charts and donut charts show how categories contribute to a whole, particularly when there are five or fewer categories. As the number of categories increases, differences become more difficult to compare and interpret. In many situations, a bar chart provides a clearer and more accurate comparison. Examples The following examples illustrate different types of data visualizations but do not represent every way each type can be designed or presented. Data attribution The maps and selected charts in this guide use King County Food Establishment Inspection Data from 2022 to 2025. Data provided with the permission of King County. This attribution does not apply to the histogram, heat map, or infographic examples.
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