What is a bar chart?
A bar chart displays information (data) by using rectangular bars of different heights.
A bar chart has a vertical axis with numbers on it, and a horizontal axis showing values of something that has been investigated.
Using bar charts to record data in primary school
As part of teaching data handling, teachers will usually ask children to investigate something by asking the other children in their class about it. This could be a favourite fruit, cake, animal or country. Older children may be asked to investigate opinions about something, for example school dinners or school uniform. Children then record the information they find using a tally chart.
Pictograms are used in Key Stage 1 to introduce children to bar charts.
The next step is for children to colour in blocks on a ready-made axis to show information they've gathered:
In Key Stage 2 children will start to produce their own bar charts on squared paper.
- First they need to think about what is going to go on each axis.
- They then need to look at their numbers and make sure their vertical axis goes up as high as the biggest number.
- They need to work out whether the numbers on the vertical axis are going to go up in 2s, 5s or 10s and position the numbers correctly.
- They then need to work out how wide each bar needs to be. (It is very important that bars are drawn all the same width).
Children need to be able to interpret bar charts by answering various questions. Example questions might be:
How many more children liked bananas than oranges?
Which was the least popular fruit?
How many children were asked altogether?
They also need to be able to produce bar charts on a computer. Usually, teachers will dedicate a few ICT lessons to showing children how to produce bar charts relating to information gathered in a maths lesson.
Later on in Key Stage 2, children need to start producing bar charts with grouped discrete data.
This bar chart was drawn up after a class of Year 6 children recorded data on the heights of everyone in the class. Instead of having a bar for every single measurement, they instead grouped the measurements. Children in Year 6 would need to be able to understand this bar chart and also be able to gather and present data in a similar way.
Children may be asked questions similar to the following about a bar chart like this one:
Kathleen is 142cm tall. She said: 'I am in the most common height range in the class.' Is she correct?
Robert is 132cm tall. He said 'I am the shortest child in the class.' Is he correct?