Types of graphs
You may have heard your child talk about working on their data handling skills at school. This often involves them looking at, interpreting and making their own graphs.
There are several types of graphs in maths and the following are the main ones used at primary-school level.
Types of graphs: Pictograms
Pictograms are usually introduced as children move through Years 1 and 2. This type of graph is a fun and engaging way to start learning about data handling. Pictograms use pictures or symbols to show the data. For example, if children were asked to draw a graph of their favourite fruits, they might use a picture of an apple to represent each vote for apples. Pictograms are a great way to visually compare data and start discussions about more, less and equal amounts.
Here is an example of a pictogram:
To help your child with learning about these at home, why not do some counting such as the number of different fruit in the fruit bowl or create a simple pictogram to track the weather. Each day, your child can draw a symbol representing the weather (a sun for sunny days, a cloud for cloudy days, etc.) on a chart. This can help them understand how pictograms represent data in a visual way.
Types of graphs: Bar charts
Bar charts, or bar graphs as they are often called, take things a step further and are generally introduced to children during Year 3 of their primary curriculum. They use rectangular bars (either vertical or horizontal) to represent data. The length or height of the bar corresponds to the amount of data it represents.
Here is an example of a simple bar chart:
Bar charts are great for comparing different categories of data. For example, children might use a bar chart to show the number of pets owned by other children in their class, with different bars representing different types of pets. Children in Year 3 will also be asked to look at bar charts and answer questions about the data they contain.
If you are wanting to help your child learn about this type of graph at home, help them to look for different examples of data they could count and record. For example, you could create a bar chart to track the number of different coloured cars you see on a walk or a drive. Each time you see a car, your child can add to the bar representing that colour on the chart. You can then pose them questions about the data such as “How many red cars did we see?” This can help them understand how bar charts can be used to compare different categories of data.
Types of graphs: Line graphs
Line graphs are the next stage up in complexity and are often taught during the end of Year 4 and as children move into Year 5. They often feature in the Year 6 SATS too, so it is well worth your child getting to grips with these.
Line graphs are used to show changes over time. They're made up of points connected by lines. For example, children might use a line graph to track the temperature over a week, with each point representing the temperature on a different day. Line graphs are great for showing trends and patterns in data. Teachers will often test understanding of data by asking children to look for patterns or trends that can be seen on a line graph.
Here is an example of a line graph that may be used in a Year 5 maths lesson:
When working on these at home with your child, you could create a line graph tracking the temperature or the number of daylight hours over a week or a month. Each day, your child can add a new point to the graph. This can help them understand how line graphs can show trends and patterns.
Types of graphs: Pie charts
Probably the most sophisticated type of graph taught within the Primary National Curriculum are pie charts. These are usually introduced during Year 6 as children have a much greater understanding of circles, circumference, percentages and degrees – all of which are important to know when making our own pie charts.
Pie charts are used to show parts of a whole. They're circular charts divided into sectors (like slices of a pie), with each sector representing a portion of the total. For example, children might use a pie chart to show how they spend their time in a typical day, with different sectors representing different activities.
Here is an example of a pie chart from a Year 6 lesson:
In understanding how pie charts work, it is vital for children to know that a pie chart represents a whole — that could be a whole group of people, a whole amount of time, a whole collection of things, etc. The whole is represented by the entire circle of the pie chart. When drawing their own pie charts, they must first calculate the fractions. Each slice of the pie represents a part of the whole. To figure out how big each slice should be, you need to calculate what fraction of the whole it represents.
For example, let's say you're making a pie chart of favourite fruits among a group of 20 people. If 5 people chose apples as their favourite fruit, then the fraction of the group that chose apples is 5 out of 20, or 5/20. It's often easier to work with fractions when they're in their simplest form. In this case, 5/20 simplifies to 1/4. This means that 1/4 of the group chose apples as their favourite fruit.
What about percentages? Often pie charts, like the one above, are drawn using percentages. Therefore, it can be necessary to convert your fraction to a percentage. To do this, divide the top number of the fraction (the numerator) by the bottom number (the denominator), then multiply by 100.
In the example of the fruit we have spoken about, 1 ÷ 4 = 0.25, and 0.25 x 100 = 25. So, 25% of the group chose apples as their favourite fruit. We then need to determine the angle to draw. A full circle is 360 degrees, so each slice of the pie chart is a certain number of degrees of the circle. To find this, multiply the percentage by 360. For the apple slice, you would calculate 25/100 x 360 = 90 degrees.
Why are graphs important?
Each of these types of graphs gives children a different way to look at data, helping them to understand and interpret information in a visual way. As they progress through school, they'll learn to use each type of graph to best represent the data they're working with. It is inevitable that they will come across questions in assessments or the national SATS where they will either have to draw, complete or analyse the data held within one of these graph types.
Remember, you can support your child's learning at home by finding opportunities to use these types of graphs in everyday life. Whether it's charting the weather with a line graph, or using a bar chart to keep track of foods in the cupboard – there are plenty of fun and practical ways to bring graphs to life!