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.
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
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.
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