Cropped graphs

Graphs can also be misleading if large sections are cropped off. The bar graph to the right is an instance of this deceptive practice. It shows the results of a poll in the US that asked people whether they agreed or disagreed with a particular court’s decision. Here, the bottom sections of the bars and the bottom section of the vertical axis have been cut off. This has created the impression that there is a lot of support for the court’s decision among Democrats, but very little support among Republicans and Independents. Yet the difference between the levels of support between Democrats and Republicans/Independents is only 62% - 54% = 8%.

The bar graph to the right shows how the original graph would have appeared if the bottom sections of the bars had not been cut off. Here you can see that the difference in the support for the court’s decision between Democrats, Republicans and Independents is actually quite small. As you can see, it is quite easy to be fooled when large sections of a graph are cut off. But don’t despair. You can easily know when someone is using this trick by checking if the scale starts at some number other than 0. For instance, the above graph started at 53, not 0.

Discussion

The above bar graph shows the top tax rate that would prevail under the tax plan of some presidential candidate.

Has the author used cropping in this instance? If so, how?
Explain how this could be misleading.
Redraw the graph so that it is not misleading.

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Cropped Graphs (Investigation)