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Using Visual Aids: Graphs

Bar Graphs

Bar Graphs are used to show trends over a period of time. The most helpful aspect of bar graphs is the fact that they show volume in the form of a bar, which suggests a physical quantity: the longer the bar, the greater the value. This visual aspect is why bar graphs have such an impact on their audience. There are two types of bar graphs, and both allow the creator to show more than one type of data in the graph.

Bar graphs may be either simple or multiple and either vertical or horizontal. A simple bar graph only has one bar per column label. A multiple bar graph has more than one bar per column label.

A vertical bar graph is often called a column graph and a horizontal bar graph is usually just referred to as a “horizontal bar graph.” Column graphs are used for comparing values. However, they do have a couple of disadvantages. When the written label at the foot of each bar is too lengthy, column bar graphs become confusing. In this case, it is best to use a horizontal graph instead because lengthier category labels can be displayed in their entirety on a horizontal bar graph’s rows. Legends may be used, but it is best if you have four or fewer colors of bars. The following example to the left shows a column, or vertical bar graph.

Texas General Store Profits is a simple vertical bar graph while Recorded Tutoring Sessions is a multiple vertical bar graph.