A bar chart is one of the tools used to represent statistical data in a comprehensive format. It is usually plotted on a graph ion order to fully show the scales for each item of data represented. A bar chart is made up of bars placed on the horizontal axis, plotted against values on the vertical axis. The height of each bar usually is determined by the size of the commodity it is representing.
Each bar stands separately on its own and there is equal space that separates one bar from the other. Using a bar chart to represent statistiscal data makes it very easy to compare various values in a given project. The type of data that can be represented with a bar chart varies, including the population of an area, scores of students, staff departments in an organization, age distribution and other commodities. Once correctly plotted, a bar chart can easily be used to analyze and compare different data in a set of values.
Now I will demonstrate how to use a bar chart to represent data in graph. Lets look at the first example.
Example 1: The number of staff spread across various departments of an institution is as follows: Marketing 400, Engineering 250, Statistics 100, Nursing 50, Food sciences 200, Medicine 500.
(i) Represent the information in a bar chart
(ii) How many staff are there in total
(iii) If a staff is randomly selected, what is the probability that he is from Medicine department.
(iv) How many staff are found in each department on the average?
Solution:
(i) Represent the information in a bar chart
Using the information provided, I will draw a table first. Then I will draw the bar chart. Below is the table.
| Department | Number of staff |
|---|---|
| Marketing | 400 |
| Engineering | 250 |
| Statistics | 100 |
| Nursing | 50 |
| Food Sciences | 200 |
| Medicine | 500 |
And now, here is the bar chart below:
(ii) How many staff are there in total?
We simply need to add all the figures given.
Total staff: 400+250+100+50+200+500 = 1500.
(iii) If a staff is randomly selected, what is the probability that he is from Medicine department.
We just have to do a fraction of Medicine staff figure over the totals.
Probability of Medicine = 500/1500 = 1/3
(iv) How many staff are found in each department on the average?
We will simply divide the total by the number of departments represented.
Average number of staff: 1500/6 = 250 Staff.
Bar charts make it easy to represent statistical data in a meaningful way. The bars represent each commodity and the height of each bar is represents the size of that commodity. Once you get the figures right, you can use an online tool or a graph to plot and draw the bar chart. We will see more examples later.
