Bar diagrams are one of the easiest and the most commonly used devices for presenting business and economic data. They are especially good for the purpose of visualizing categorical data or time series data in statistics.

A limitation of the simple bar diagram is that it can be used to portray only a single characteristic or category of the data. If two or more sets of inter-related phenomena or variables are to be presented graphically, then we draw a multiple bar diagram. For example, if we wish to draw a bar graph showing the number of students enrolled in a school over a period of six years we can represent the information with a bar diagram. But if we also want to take into account the sex distribution of students then a multiple bar graph should be used.

**Definition of Multiple Bar Diagram:**

A multiple bar graph is nothing but a usual bar graph except for the fact that each category has two or more bars – one for each subdivision. For instance, if we plot the population of a country over a period of five years we can draw two bars for each year – one showing the number of females and the other bar showing the male population. The diagram below shows an example of a multiple bar graph.

**How to draw a Multiple Bar Diagram:**

- Plot the categories on the X axis.
- For each category, draw a set of bars adjacent to each other. Here, each bar corresponds to a particular subcategory (such as male/female).
- The corresponding numerical values are plotted on the Y axis.
- The height (length) of the rectangles or bars are taken proportional to magnitude of the observations.
- To distinguish between the different bars in a set different colours should be used. This makes the diagram easier to read and more visually pleasing.

**Example 1:**

Consider the diagram below showing the yearly profits of two companies over a period of time. From the below diagram, we can see that Company A made a profit of 120000 dollars in the year 1944-95 whereas, Company B made a profit of 90000 dollars in the same fiscal year.

We can draw the following conclusions by looking at the graph above:

- The profits of both of the companies increases consistently year to year.
- Company A always makes a greater profit than company B each year.

**Example 2:**

Consider the diagram below showing the population of students in a school in the eighth, ninth and tenth grades.

We obtain the following information from the above graph:

- There are 30 boys and 20 girls in the eight grade in the school.
- There are 40 boys and 30 girls in the ninth grade.
- There are 45 boys and 35 girls in the tenth grade.

We can draw the following conclusions by interpreting the graph:

- Since the blue bars are always higher than the red bars, we conclude that there are more boys compared to girls in each grade.
- There are more students in the grade 10 compared to grades 8 and 9. There are more students in the higher grades compared to the lower grades.

**Advantages and Disadvantages of Multiple Bar Graph:**

The advantage of a multiple bar graph is that it can be used to compare two or more variables within a given data set. The information regarding two or more variables is available side by side in a single diagram. There is no need to draw two separate diagrams. Another merit of the multiple bar graph is that it is very easy to interpret and looks visually appealing.

The disadvantage of a multiple bar graph is that it cannot be drawn if there are too many subcategories/variables in the data. This is because we cannot fit too many bars into a single diagram.

**Related Articles:**

- Advantages and Disadvantages of Histogram.
- Pareto chart- How is it different from a standard vertical bar graph?
- Horizontal Bar Graph – Explained with Examples.