If you work through this section you should be able to:
This section assumes you have some understanding of the different kinds of chart that can be used and why (see Introduction to charts section).
You may also find the Interpreting charts section useful.
A chart is used to display data in a graphical format that makes it easy to read the data at a glance. Where a table simply presents raw data, a chart can highlight the trends and changes in data series and the relationships between different sets of data. Using a chart can make relationships between data clearer and give greater visual impact. They are often used to illustrate arguments about the meaning behind figures and statistics, as they can make data relationships more dramatic.
When you create a chart you should remember to:
Have a go at the activities that follow before going on to see the explanations for each activity.
Using the data in the table below, complete the column chart that follows. You can either print out this page or copy the chart onto paper.
| Crops | Fraction | Percentage | Actual square kilometres |
|---|---|---|---|
| Oats | 1/8 | 12.5% | 25 |
| Grass | 1/4 | 25% |
50 |
| Barley | 3/8 | 37.5% | 75 |
| Wheat | 1/4 | 25% |
50 |
| Crops | Fraction | Percentage | Actual square kilometres |
|---|---|---|---|
| Oats | 1/8 | 12.5% | 25 |
| Grass | 1/4 | 25% |
50 |
| Barley | 3/8 | 37.5% | 75 |
| Wheat | 1/4 | 25% |
50 |
The column chart shows square kilometres, so it is the square kilometres column in the table that we are interested in. We already have the columns for oats and grass so we need to know the information for barley and wheat.
Barley - 75 sq km
Wheat - 50 sq km
Then all we need to do is draw a vertical column for barley that goes up to the 75 mark and one for wheat that goes up to the 50 mark. We also need to colour or pattern these differently from the two columns we already have, as we want to be able to clearly differentiate between them. The new columns also need to be labelled.
400 people were asked how they would vote if a general election were called. The following table shows the number of people who voted for each of five categories.
| Conservative | Labour | Lib-Dem | Others | Undecided / Don't Care | |
|---|---|---|---|---|---|
| Number | 98 | 108 | 65 | 17 | 112 |
| Percentage | 24.5% |
Percentage = (number ÷ total number) × 100%
For example: Percentage Conservative voters = (98 ÷ 400) × 100% = 24.5%
| Conservative | Labour | Lib-Dem | Others | Undecided / Don't Care | |
|---|---|---|---|---|---|
| Number | 98 | 108 | 65 | 17 | 112 |
| Percentage | 24.5% | 27% |
16.25% |
4.25% | 28% |
Once you know the percentages of each value it is easy to draw a rough estimate of the sections in the pie chart.
If you need to be very exact with your pie chart, you will need to work out exactly how many degrees should be allowed for each segment. A circle is 360°(degrees), so for the Conservative section you would need to work out 24.5% of 360°. If you are drawing the chart on paper, you will need a protractor to measure the degrees.
You can find more information about percentages and fractions in the Percentages and ratios and Fractions sections of this site.
When you create a column chart you should remember to:
Did you remember to label the charts and give them titles? For pie charts this means writing not only what each segment represents (Labour, etc.) but also the percentage value. Rather than labelling the actual columns/segments as in the example above, you may have drawn a 'key' to show what each represents.
Did you remember to give a different pattern or colour to each data series?
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