A double bar graph is a chart that uses parallel bars at proportional lengths that represent quantitative values. The length of the bar correlates with the data.
The bars on a double bar graph can be placed vertically or horizontally. Often, a bar graph has an axis that is labeled with categories and an axis labeled with numerical values. Bar graphs represent categorical data. For example, the labels can be countries, genders, age groups, races or time periods.
A double bar graph uses discrete values. The chart is made large enough to fit all of the data for each category.