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Graphic arts

Graphs can show us things more clearly than words do and allow us to put large amounts of information on a simple diagram. For example, the graph (below) of coal consumption in the UK shows clearly that that consumption has fallen. If we were to provide the data in a table or in words it would be less clear and take much longer to read. Another point to consider is why we use a particular type of graph. The questions and answers on this page will show you.

Figure 1
Coal consumption in the UK
Figure 2
Pie chart showing the changing markets for coal

Question 1 Using Figure 1 and Figure 2 show how the market for coal has changed between 1950 and 1993 (4 marks).

Answer The market for coal has fallen between 1950 and 1993. We can make an educated guess about consumption in the 1950s from the trend of the graph in Figure 1. In addition, the demand has changed dramatically between 1950 and 1993. In 1950, the domestic market accounted for about one-third of the demand for coal, industry one-sixth and power stations one-sixth. By contrast, in 1993 power stations account for over three-quarters of the market for coal. This is an enormous percentage increase. However, all other users have declined: industry uses about one-twelfth and domestic residences even less.

Examiner's comments A good answer. The candidate has referred to both pieces of information, as the question asks. Moreover, she has made an educated guess which is quite plausible, ie that levels of coal consumption were higher in the 1950s compared with the 1990s. As for the changing demand, she has identified the main users in both charts, and commented on the scale of the change. She has used words and phrases such as "however" and "by contrast". These are excellent link words in an exam.

Question 2 What are the advantages and disadvantages of using pie charts to show the changes in demand?

Answer The advantages include clarity. Pie charts can be used for data that add up to 100 per cent. We can see how the per cent composition has changed over time. However, we are not told about the size of the market. The two pie charts suggest that the size of the market is the same in both years. One way round this would be to have the size of the circle proportional to the size of the market.

Examiner's comments Spot on. The student has read the question properly and given the good points and the bad points. She has gone even further and suggested how the diagram could be improved.

Figure 3
The number of collieries and their output

Question 3 Comment on the information shown in Figure 3, the number of collieries and their output. Why have bar charts been used? (5 marks)

Answer The number of collieries, output of coal, and the size of the workforce have all declined since 1955, but not at the same rate. The number of collieries has declined the most, over 90 per cent, from about 850 in 1955 to about 20 in 1994. The workforce has also declined by a huge amount, from 700,000 to well under 50,000. By contrast, the output has declined the least, about 50 per cent, from 200 million tonnes to 100 million tonnes. Bar charts are useful here as they show a cross-section of the coal industry at four particular times and allow us to compare these times.

Examiner's comments There are four or five good points here, and they are supported with evidence from the graphs. There is also a good use of language, and the student compares the decline of the three features very well. She has also made use of the scale to work out some of the answers.