Bar charts display data as bars, the size of the bar shows us the value of the data.
Here is a bar chart showing the number of moons that five planets have:
In this bar chart the size of the bar tells us how many moons each planet has. The size of the bar can be read off against the scale on the left.
When you have a bar chart in front of you on a sheet of paper it is easier to follow the top of the bar across to the scale on the left to see the value it is showing. You can even place a ruler along the top of the bar and see where it meets the scale.
It is a good idea to take a look at the scale of the bar chart and make sure you understand how it works. This one is easy as each step up the scale represents 1 moon and the scale is labelled every 5 notches. But some bar charts have more complicated scales and steps could be in 2 or more.
If you look at the bar for Earth it is very short. It just goes up to the level of 1 on the number of moons. This tells us that Earth has 1 moon.
If you look at the bar for Neptune and follow the top of it across to the scale on the left you can see that it falls 1 below 15 at 14. So Neptune has 14 moons.
Mercury has no bar at all! This just means it has no moons.
Line graphs show data plotted on a graph that is connected by a line. You can read off values using the line.
If we want to know what the temperature was on Tuesday we can find ‘Tuesday’ Labelled at the bottom, follow up to the line and then across to the scale, and we see that it was 4°C on Tuesday.
On Friday it was 23°C. You just move up from the day until you reach the line and then move across to the scale.
A pie chart looks like a big round pie with different size slices shown on it!
The size of the slice tells you the size of that data compared to the other slices.
One hundred children at the International Space School were asked what their favourite sport was. Here is a Pie Chart showing their answers:
The colours on the chart are shown on the right of the chart with labels telling us which ‘slice’ of the pie relates to which sport.
If you were asked how many children’s favourite sport was ‘Asteroid Cricket’? You have to judge the percentage, or fraction of the pie chart that is taken up by this slice of the pie. We can see that ‘Asteroid Cricket’ is the blue slice. It takes up 50% of the pie. So we know half of the children gave this as their favourite sport.
We can give an exact value to this because we were told that in total 100 children had been asked their favourite sport.
50%, or half, of 100 children is 50 children.
If you were asked how many children said ‘Lunar Hockey’ was their favourite sport, you need to look at the purple ‘slice’ and judge it’s size. It takes up 25% or one quarter of the pie. 25% of 100 is 25. So 25 children said ‘Lunar Hockey’ was their favourite sport.
Pictograms use pictures to show ‘how many’.
There is no scale on the side so you just need to count the pictures to see ‘how many’ there are of each.
Here is a pictogram showing the number of eggs laid by Henrietta the hen:
If we were asked, how many eggs did Henrietta lay on Monday?
We just count the number of eggs – there are 6.
If we were asked how many eggs did she lay on Friday?
Just count the egg pictures next to Friday – she laid 3 eggs.