Graphs and maps

Graphs: part 1

Graph	Use it for	Common mistake
	Comparing amounts in categories, such as land uses	Uneven gaps or bars of different widths
Line graph	Change over continuous time or distance	Joining points that aren't continuous, such as separate countries
Pie chart	Parts of a whole, as percentages	Forgetting each 1% is 3.6° of the circle
	Grouped continuous data, such as pebble sizes in classes	Leaving gaps between bars: they should touch

Reading them: read the axis titles and units first, then the overall pattern, then the highest, lowest and any exceptions, with figures.

Key terms

Graphs: part 2

Use it for	How to read it	Common mistake
Testing a relationship between two variables	Look at the direction of the best-fit line: positive, negative or no correlation	Saying one causes the other just because they are linked
Monthly rainfall (bars) and temperature (line)	Read each axis on its own side	Reading temperature against the rainfall axis
Males and females in each age group	Wide base: many young people; wide top: many old people	Mixing up the male and female sides

Key terms

Maps

Map	Use it for	Common mistake
Choropleth	Data for areas, shaded darker for higher values	Using unrelated colours instead of shades of one colour
	Lines joining equal values, such as contours or rainfall	Lines that cross: they never should
Dot map	Distribution, each dot standing for a number	Forgetting to say what one dot represents
Desire-line	Journeys from origin to destination, as straight lines	Drawing the route taken, not a straight line
Proportional symbol	Values at points, the symbol's size showing the value	Symbols overlapping so they can't be read
Flow-line	Movement along a route, the line's width showing the amount	Widths not to scale

Reading them: use the key, then describe the pattern with places and values.

Key terms

Exam practice

Plan your own answer first, then open the model answers to see what each level looks like.

4 marks · about 4 minutes

Explain why a scatter graph suits testing a hypothesis such as "River velocity increases downstream".

Explain means: Give the reasons why something happens, developing each point with "because" or "so".

Level 1 (Basic)· 2/4 marks (band 1–2)

A scatter graph shows two things at once, so it is good for this.

Why this level: A correct basic idea, but not developed. To reach Level 2: explain what the two variables are, how a best-fit line shows the relationship, and how anomalies show up.

Level 2 (Clear)· 4/4 marks (band 3–4)

The hypothesis is about a relationship between two variables, distance downstream and velocity, so each site can be plotted as one point. A best-fit line shows whether there is a positive or negative correlation, so you can see whether the hypothesis is supported. Anomalies also stand out, far from the line, so they can be explained.

Why this level: A clear, developed explanation linked to the hypothesis. Full marks.

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