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.
Table 3: Number of staff in an organisation
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.