What Is a Bar Chart?
A bar chart (or bar graph) is a chart which uses bars to present data.
The height of each bar shows how often each value appears in the data.
The Oxford English Dictionary defines a bar chart as "a statistical diagram in which numerical quantities are represented by the height or length of rectangles of equal width, drawn usually side by side along an axis."
A Real Example of a Bar Chart
The image below shows a bar chart. It represents the test scores of a class of students:
We can find out what test scores the students achieved by reading off from the bar chart.
Reading from a Bar Chart
Reading from a bar chart is easy. The height of the bar above each test score tells us how many students achieved that test score.
The blue bar is above a Score of 5. It has a height of 2 (as measured on the Frequency axis).
This means that 2 students have a test score of 5.
The orange bar is above a Score of 6. It has a height of 3.
This means that 3 students have a test score of 6.
The green bar is above a Score of 7. It has a height of 2.
This means that 2 students have a test score of 7.
Creating a Bar Chart
Creating a bar chart is easy. We need to know how many times each value in a set of data appears.
It is useful to create a frequency table of the data first and then create a bar chart from it.
Bar Charts and the Types of Data
Bar charts can present the different types of data.