Effective ways of displaying information

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# 1.4 Bar charts

A bar chart is another way of presenting data. It is designed to show frequency distribution, for example, the number of staff in each of four categories in an organisation. You could present the data given in Table 6 in a bar chart as shown in Figure 6.

## Table 6: The composition of staff in an organisation

 Senior managers 20 Other managers 30 Administrative 70 Clerical 80 Total 200
Figure 6: Composition of staff – a bar chart

You can see how the bar chart has been created. The four categories are marked on the horizontal axis, so the chart is built on that axis. An appropriate number scale is marked on the vertical axis. A vertical bar is drawn for each of the categories. The height of each bar represents the number of staff in that category. The width of each bar is the same. In the resulting chart we can see that the bar representing ‘Senior managers’ measures 20 on the vertical scale; that representing ‘Other managers’ measures 30; that representing ‘Administrative’ measures 70; and that representing ‘Clerical’ measures 80.

Of course, you can show more than one set of data on a bar chart. Suppose that you wanted to present the data shown in Table 7.

## Table 7: The composition of staff in an organisation

Year 1 Year 2
Senior managers 20 35
Other managers 30 25
Clerical 80 130
Total 200 250

Then the bar chart could be shown as Figure 7(a) or as Figure 7(b).

Figure 7(a): Composition of staff in Years 1 and 2 – bar chart
Figure 7(b): Composition of staff in Years 1 and 2 – bar chart

Notice the difference between the two bar charts. In Figure 7(a) the dominant relationship, the one that will catch the reader's eye, is the one between the four categories in each of the two years. The emphasis remains on the composition of the whole staff in each of the years. In Figure 7(b) the dominant relationships are between each of the four categories. If you wanted to emphasise how the numbers in the four categories had changed during the two years, you would choose the type of representation shown in Figure 7(b).

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