Bar Charts
What is a bar chart?
- A bar chart is a way to represent qualitative or discrete data
- Colours of car, shoe size, names of students, etc
- The vertical axis shows the frequency
- The scale should start at zero and go up in equal amounts
- The horizontal axis shows the different options
- Bars are used for each option and the height is the frequency
- Each bar should have the same width
- There should be gaps between each bar
What are bar charts used for?
- You can easily identify the mode using a bar chart
- The mode is the most common outcome
- This will be the outcome with the highest bar
- You can use a comparative bar chart to compare two (or more) sets of data
- For each outcome you would have a bar for each set of data to show the frequencies
- The bars for one option would be side-by-side with no gaps
- You would use colours or shading and a key to clearly show which bars belong to which sets of data
Worked Example
Mr Barr teaches students in both Year 7 and Year 8. He records the number of pets that students in each year have and uses a bar chart to represent this information.
a)
Write down the mode for the number of pets for the Year 7 students.
b)
How many Year 8 students are there altogether?
a)
The mode for Year 7 is one pet as that has the highest bar.
b)
4 + 8 + 4 + 3 + 0 + 2 = 21
