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If you want to present the math marks obtained by students in a class graphically, then a bar graph will always be a good choice as it helps in comparing the data visually. But if you want to present marks obtained in one more subject and want to compare it with the marks obtained in math, then the choice will be a double bar graph.

Let’s understand what is a double bar graph and how is it read and drawn using examples.

## What is a Double Bar Graph?

A double bar graph is a graphical display of information using two bars beside each other at various heights. The bars can be arranged vertically or horizontally. We use a double bar graph to compare two data groups.

Similar to a bar graph, a double bar graph is also drawn over two axes. The $x$-axis of a double bar graph shows the categories being compared, and the $y$-axis represents the scale. A scale is a set of numbers that represents the data organized into equal intervals. The title of the double bar graph provides a general overview to the reader of what is being measured and compared. A double bar graph also has a key. The key for a double bar graph represents the groups being compared with two separate colours or shades.

The graph shown below is a vertical double bar graph.

The double bar graph can also be a horizontal double bar graph. In the case of a horizontal double bar graph, the $x$-axis represents the scale showing the data and the $y$-axis shows the categories being compared.

## How to Read a Double Bar Graph

The different steps to read a double bar graph are given below:

**Step 1:** Check whether the given double bar graph is a horizontal double bar graph or a vertical double bar graph.

**Step 2:** In the case of a vertical double bar graph, the categories are present on the horizontal axis (or x-axis) and the data values are represented by the vertical bars(or rectangles).

In the case of a horizontal double bar graph, the categories are present on the vertical axis (or y-axis) and the data values are represented by the horizontal bars(or rectangles).

**Step 3:** For each category,

In the case of a vertical double bar graph note down the point on the $y$-axis corresponding to the height of a vertical bar

In the case of a horizontal double bar graph note down the point on the $x$-axis corresponding to the length of a horizontal bar

### Examples

Let’s consider an example to understand how to read a double bar graph.

**Ex 1:** Observe the bar graph and answer the following questions.

- Which is the least preferred sport of the girls?
- Which is the most preferred sport of the boys?
- How many girls like cricket?
- Which sport is liked by 10 girls?
- How many students like basketball?

The smallest bar corresponding to girls is football, therefore, the least preferred sport of girls is football.

The largest bar corresponding to boys is cricket, therefore, the most preferred sport of boys is cricket.

The number of girls liking cricket is 20.

Students include both boys and girls.

The number of boys liking basketball is 20 and the number of girls liking basketball is 25. Therefore, the number of students liking basketball is 45(20 + 25).

## How to Make a Double Bar Graph?

Let’s now understand how to make a double bar graph. To make a double bar graph, the steps are:

**Step 1:** Make a data-filled table

**Step 2:** Draw the horizontal axis and vertical axis. (For example, Favourite Food)

**Step 3:** Now, label the horizontal axis.

**Step 4:** Write the names on the horizontal axis, such as Pizza, Noodles, Pasta, and Burger.

**Step 5:** Now, label the vertical axis. (For example, Number of Students)

**Step 6:** Finalise the scale range for the given data. Since the number 45 is the highest value while 0 is the lowest. This graph should be scaled such that 1 unit equals 5 students.

**Step 7:** Finally, draw the bar graphs that should represent each category of the fruit with their respective numbers.

### Examples

**Ex 1:** Given below is the data showing the favorite fast food of boys and girls of a class. Draw a Double Bar graph representing the given information.

The first step is deciding the title of the bar graph. Let’s name our bar graph “Favourite Fast Food of Students”.

Next, draw the axes.

The horizontal axis represents the activity and the vertical axis represents the number of students.

To choose an appropriate scale, note down the minimum and maximum values in the data set.

The minimum value (Number of boys for pasta = 10)

The maximum value (Number of boys for noodles = 35)

Since the maximum value is 35 and the minimum 10, so let’s mark the maximum point on the vertical axis as 35 starting from 0 with equal intervals of 5. This will fit all the values properly in the bar graph.

Finally, draw the bar graph that should represent each category of the activity with their respective numbers.

## Practice Problems

Draw a Double Bar Graph to compare the favorite ice cream flavors of girls and boys in a class.

Draw a double bar graph to compare the marks of the students in practice tests and tests.

Draw a double bar graph to compare the number of boys and girls in different classes.

## FAQs

### What is a double bar graph?

A double bar graph is a graphical display of information using two bars beside each other at various heights. The bars can be arranged vertically or horizontally. We use a double bar graph to compare two data groups.

### What is the difference between a bar and a double bar graph?

A bar graph is a graphical display of data using single bars of various heights. A double bar graph is a graphical display of information using two bars beside each other at various heights. The bars can be arranged vertically or horizontally. We can use a double bar graph to compare two data groups.

### Why double bar graph important?

Double bar Graph helps us to compare two data groups. For example, we want to compare the marks obtained by boys and girls separately in class in different subjects.

## Conclusion

A double bar graph is a graphical display of information using two bars beside each other at various heights. The bars can be arranged vertically or horizontally. Its importance lies in the fact that it facilitates the comparison of two different categories.