A double bar graph is a bar graph used for displaying two sets of frequency data for each data group. It can be used to make comparisons between and within data groups. Data displayed on a double bar graph is countable.
When making observations from a double bar graph, information may be obtained from the differences between the two data bars within one group as well as the height of the individual bars. Double bar graphs are constructed in the same manner as single bar graphs. The horizontal x-axis displays information obtained during a particular time period, and the vertical y-axis displays the quantity of information being measured.