Numeracy, Maths and Statistics - Academic Skills Kit

Bar Charts

ContentsToggle Main Menu 1 Definition 2 Reading Bar Charts 3 Worked Example3.1 Video Example 4 Creating Bar Charts4.1 Video Examples 5 Workbook 6 Test yourself

Definition

A bar chart is a way of showing the distribution of data with a discrete data set. Bar charts can be represented horizontally or vertically, they can also represent more than one set of data. One axis is labelled with the category/group and the other labelled with the frequency of the category/group. They are usually drawn with no gaps between the rectangles. However, when the data ranges share a border, when the data is categorical the bars are usually drawn with gaps in between. The length of each rectangle is proportional to the category it represents.

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Reading Bar Charts

Worked Example

180 people were surveyed and asked which day of the week was their favourite. The results are shown on a bar chart below.

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a) What is the mode of the data? b) How many more people prefer Fridays to Wednesday? c) Are there more people who prefer Tuesday than people who prefer any day other than Tuesday?

Solution

a) The mode is the day most frequently chosen as people's favourite day of the week. This can be seen by the bar which is the longest, in this case Tuesday. As you can see there are five segments between $50$ and $60$; every segment represents two people. Draw a line from the top of the bar representing Tuesday across to the $y$-axis, and read off the value. The modal day is Tuesday and it is $56$ people's favourite day of the week.

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b) Read off the graph how many people voted Wednesday as their favourite day of the week and subtract this from the number of people who voted Friday as their favourite.

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\[15-12=3\]

So there are $3$ more people who prefer Fridays to Wednesdays.

c) To find the number of people who prefer any day other than Tuesday you need to take the number of people who do prefer Tuesdays away from the total number of people surveyed. This is easier than adding up the total number from each bar (not including Tuesday). You know from example 1 that the number of people whose favourite day is Tuesday is $56$. So the number of people whose favourite day is anything other that Tuesday is

\[130-56=74.\]

Video Example

This is Khan Academy's example on how to read bar charts.

Creating Bar Charts

Video Examples

Example 1

This is a video on creating bar charts produced by Alissa Grant-Walker

Example 2

This is Khan Academy's video on creating bar charts.

Workbook

This workbook produced by HELM is a good revision aid, containing key points for revision and many worked examples.

Descriptive statistics including work on bar charts.