When bar diagrams are drawn in different sets, or groups to represent two or more aspects of data, it is a case of multiple bar diagrams. Such diagrams are also known as compound bar diagrams which are drawn when comparison is required to be made between any two or more aspects of a data viz. male, female, and children aspects of population, or Arts, Science, and Commerce, aspects of students strength, or married, unmarried, and widowed aspects of certain agers. However, in the interest of decency, it is advisable to exhibit at best three aspects of a data through this type of diagram, else, it may make the diagram look ugly.
The technique of drawing a multiple bar diagram remains the same as that of a simple bar diagram except that the separate bars are drawn on a common scale for each aspect of the data. Such separate bars are kept closed to each other under a set, and are decorated with different colours, dots, or shades to distinguish them from each other. Each set, or group of such diagrams is shown at equal distance on the base line which may be drawn either horizontally, or vertically. Further, some space of equal magnitude may be provided in between the bars of each of the sets.