Effective ways of displaying information

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# 1.2.1 Selecting the scales

The scales that are used determine the look of the graph. For example, if the horizontal distance between ‘Year 1’ and ‘Year 6’ shown in Figure 2 were doubled, the line would be stretched to double its present length. If the horizontal distance were halved, then the length of the line would be halved. Each of the graphs would be mathematically correct.

Now suppose that you had to draw a line graph of the staff in a second organisation using the data shown in Table 3. Figure 3(a) and Figure 3(b) show two ways of presenting the data.

## Table 3: Number of staff in an organisation

 Year 1 2 3 4 5 6 Total 200 220 240 255 270 260
Figure 3(a): Number of staff – a time series line graph (small scale, compressed)
Figure 3(b): Number of staff – a time series line graph (small scale)

Although both of the line graphs are mathematically correct, they look different. The effect, in Figure 3(a), of beginning from zero has been to compress the data shown on the y axis (from 200 to 260) and so make it harder to understand the graph. In Figure 3(b) the vertical scale begins at 200 and the scale has been extended so that the information presented in the graph is much clearer.

The presentation of data – the ‘picture’ of the data that is presented in a graph – varies according to the scales selected. Choose scales that are appropriate. As you examine a graph, pay particular attention to the scales.

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