2.13: Diagramme à barres multiples
As the name suggests, a multiple bar graph is the same as a bar graph but has multiple bars to depict relationships between different data values. One can include as many parameters as possible. However, each parameter must have the same unit of measurement.
Each bar or column in the multiple bar graph represents a data value. These graphs are used primarily in interrelating two or more sets of data. The categories of different kinds of data are listed along the horizontal or x-axis, whereas frequency is listed along the vertical or y-axis. For example, consider comparing six students based on their marks in four subjects, say, Physics, Chemistry, Biology, and Statistics, then four different bars need to be drawn for each student. Depending on the heights of the bars, the data are analyzed and compared.
Though the multiple bar graph is used for most relational cases, it has some demerits, like it often requires additional explanation and fails to expose key assumptions, causes, impacts, and patterns. Sometimes, it can be easily manipulated and may give false impressions.
