3.3 The Area Principle
There’s flexibility in the mechanics of a bar chart, from picking the categories to laying out the bars. One aspect of a bar chart, however, is not open to choice. Displays of data must obey a fundamental rule called the area principle. The area principle says that the area occupied by a part of the graph should correspond to the amount of data it represents. Violations of the area principle are a common way to mislead with statistics.
The bar charts we’ve shown obey the area principle. The bars have the same width, so their areas are proportional to the counts from each host. By presenting the relative sizes accurately, bar charts ...
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