Unit 20 Section 2 : Data display
In this section we revise how to display data visually using bar charts, vertical line diagrams, pie charts and pictograms.
Example 1: Pie Chart
At the end of each half term, the students in a particular school are graded A, B or C for their reports.
The table below shows the grades awarded for one class.
Illustrate this data using a pie chart.
First we need to find out how many items of data there are: 12 + 16 + 2 = 30
Next we need to work out the angle for one item of data: 360° ÷ 30 = 12°
Now we can find the correct angles for each category, by multiplying the frequency by 12°:
Once we have the angles, and have checked that they add up to 360°, we can plot the pie chart.
We plot the categories in the order they appear in the table, turning clockwise from a vertical line above the centre:
Example 2: Pictogram and Bar Chart
Illustrate this data using (a) a pictogram, and (b) a bar chart.
A school canteen offers students a choice of burgers, sandwiches, baked potatoes or the meal of the day.
On one day the number of children making each choice was recorded; the table below shows the children's choices:
We will use the symbol to represent 20 people, which means
that the symbol will represent 10 people.
(b) Bar Chart
This is very similar to the pictogram, except vertical rectangular bars are used instead of lines of symbols.
Example 3: Vertical Line Diagram
Illustrate these results on a vertical line diagram.
The pupils in class 7C were given a short maths test. The scores are listed in the following table:
Work out the answers to the questions below and fill in the boxes. Click on the
button to find out whether you have answered correctly. If you are right
then will appear and you should move on to the next
question. If appears then your answer is wrong. Click
on to clear your original answer and have another go.
If you can't work out the right answer then click on
In some of these questions you will need to draw lines, bars or rows of symbols on a vertical line diagram, bar chart or pictogram.
To do so, click on the grid where you want the line to finish. If you want to change the position, click at a different position in the same row or column.
If you want to remove a line, bar or row of symbols, click the highest part of the line. Practise this on the
vertical line diagram in Question 2.
You have now completed Unit 20 Section 2
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Produced by A.J.Reynolds August 2008