Present geographical data using suitable graphs and maps, calculate simple statistics like the mean and percentage, and describe what the data shows

What this dot point is asking

This skill asks you to take collected data and present it clearly using the right kind of graph or map, to work out simple statistics such as the mean and percentage, and to describe what the data shows in proper geographical language. These tasks come up directly in the data-response section. The central idea is that raw data is hard to read, but the right graph turns it into a pattern you can see and explain in a sentence.

The answer

Choosing the right graph

Different data suits different graphs:

• Bar graph: for comparing separate categories, for example the number of people using each type of transport. The bars are separate and the tallest is easy to spot.
• Line graph: for continuous data over time, for example temperature through the day. The line shows trends, rises and falls.
• Pie chart: for showing parts of a whole, for example the share of land used for housing, parks and roads. Each slice is a proportion of the total.
• Located bars or symbols on a map: for data tied to places, for example traffic counts at different junctions, drawn on the map where they were taken.

Always give the graph a title, label the axes with units, and choose a sensible scale.

Calculating the mean

The mean (a type of average) summarises a set of values in one number:

It is useful for comparing groups, for example the mean number of people per hour at two sites. Remember to include the unit.

Calculating percentages

A percentage shows one figure as a share out of 100, which makes comparison easy:

For example, if 80 of 200 people use the bus, that is 40 per cent. Percentages let you compare groups of different sizes fairly.

Describing and analysing what the data shows

When you describe data, do not just repeat numbers. Use a clear order: state the overall pattern, support it with figures, then point out any anomaly (a value that does not fit). For analysis, go one step further and suggest a geographical reason for the pattern, for example "the bus is most used because it is cheap and the route passes the housing estate." Useful words include "the highest," "the lowest," "most," "least," "increases," "decreases" and "however."

Examples in context

Example 1. Presenting a Singapore traffic count. A class that counts vehicles at three junctions can draw located bars on a street map, one bar at each junction, so the busiest junction stands out at a glance. Working out the mean count per junction and the percentage of buses helps them compare sites and explain why one junction is busier, perhaps because it is near an expressway entrance.

Example 2. Showing land use in a neighbourhood. A survey of how land is used (housing, parks, roads, shops) is best shown as a pie chart, with each slice a percentage of the total area. The chart makes it easy to say, for example, that housing takes up half the area, and to analyse why a residential estate has little land set aside for industry.

Try this

Q1. State the most suitable graph to show how temperature changes through one day, and give a reason. [2 marks]

• Cue. A line graph, because temperature is continuous over time and the line shows the rise to a peak and the fall through the day.

Q2. In a survey, 30 of 120 people walked to work. Calculate the percentage who walked. [1 mark]

• Cue. $\dfrac{30}{120} \times 100 = 25\%$.

Q3. Six rainfall readings are 4, 6, 5, 9, 8 and 10 mm. Calculate the mean. [2 marks]

• Cue. Total is 42 mm; divide by 6 readings to get a mean of 7 mm.