Final answer:
To make a difference between bar heights more significant in a bar graph, a common practice is to change the vertical axis so that it includes a larger range of values.
Step-by-step explanation:
When a bar graph-maker wants to make a difference between bar heights look more significant, a common practice is to change the vertical axis so that it includes a larger range of values. By making the vertical axis taller or shorter, variations in the height of the bars appear more pronounced. This can be achieved by adjusting the scale on the vertical axis to highlight the differences between the bar heights.