1.1 A shared understanding
All representations (including graphical ones) rely on shared understandings of symbols and styles to convey meaning. Like maps, graphical representations stress some features and ignore others. As you work through this course, bear in mind that graphs are selective representations of information. When you come across different graphs ask yourself what is being stressed and what is being ignored.
In the newspapers, you are likely to find graphs used to present all sorts of information: how the number of people who are jobless or homeless is changing; how interest rates and share prices are varying; how support for different political parties has changed.
It is easy to be seduced by graphs. They have an air of authority which defies you to challenge them. After all, many graphs used by the media have been drawn from data collected by reputable survey organisations. The graphs apparently simply show trends, variations, peaks and troughs as they are. However, no graph is simply a neutral representation of facts. All graphs are drawn from some point of view, drawn this way rather than that for a particular purpose. That is to say, someone has made some choices about how the graph should look. When you are faced with just a single graph, however, the choices may not be evident. One reason for knowing about a variety of types of graph, therefore, is to be more aware of what could have been drawn, when faced with what was drawn.
So an important message is that no graph is a value-free representation. Even if the intention is to present information in as unbiased a way as possible, that is itself a point of view. But some graphs will have been drawn specifically with the intention of presenting information in a particularly favourable or unfavourable light, to convince you of an argument or to influence your decisions. So take care when you are reading graphs that you are not misled or, perhaps more to the point, so that you do not mislead yourself. And when you are drawing your own graphs, you need to be clear about how you present your information to others so that your intentions are not misinterpreted or misunderstood.
As the American writer James Thurber put it: ‘Get it right or let it alone. The conclusion you jump to may be your own.’ (James Thurber (1956) Further Fables for Our Time, New York)