Deviation bar graph

back-to-back graph, paired bar charts, population plots, population pyramids

Deviation bar graphs are simply two bar charts aligned, where one of the charts runs right to left rather than left to right.

The two charts report on the same categories but differ in terms of the respondent group or some other variable. Thus, the shared categories, such as the survey questions, are listed in the space in the middle of the two bar charts. Usually, these are constructed as bar charts, where the bars are horizontal, not column charts.

The purpose of graphing each set of responses separately from one another is so that it is easier to see the shape of each response set. Thus it is important to order one of the response sets from greatest to least so that it is easier for a viewer to see where the other response set is out of shape.


Response sets from teachers and principals

Back to back deviation bar graph showing disparity in responses between teachers and principals to a set of statements such as "school climate is positive"

Source: Stephanie Evergreen

This example shows the response sets of teachers and principals to a set of common survey questions. Principal responses are ordered greatest to least, so it becomes obvious that the teachers differed.

Advice for choosing this method

Use this method when you are looking at the overall shape of two response sets, to spot where they did not match. It is not good for comparing the responses between two groups on individual items.

Advice for using this method

Boost the ease of interpretation by colour coding the bars where the responses differ greatly between the two groups.


Other ways to compare sets of values

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