Graphs and data skills Cambridge IGCSE Geography (9–1) revision
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In plain words
Geography is full of numbers: rainfall, populations, river speeds. A graph turns them into a shape you can read. The skills are choosing the right graph, and then describing what it shows with figures.
7 things to know
- A line graph shows change over time. A bar graph compares separate categories. A divided bar, pie chart or doughnut graph shows how a whole is split into parts.
- A scatter graph shows whether two sets of data are related. A line of best fit shows the trend. A positive correlation means both rise together, and a negative correlation means one rises as the other falls.
- A climate graph has bars for monthly rainfall and a line for average temperature. A population pyramid shows age groups and sex.
- A histogram shows the frequency of continuous data in equal classes. A radial graph or rose chart shows directions, such as wind direction. A triangular graph shows three parts that add up to 100%. A kite graph shows how something changes along a line.
- A flood hydrograph shows rainfall as bars and river discharge as a line. Lag time is the time between peak rainfall and peak discharge.
- To describe a graph: state the overall trend, quote figures with units, give the highest and lowest values, and point out anything that does not fit the pattern (an anomaly).
- Mean: add up and divide by how many. Median: the middle value when in order. Mode: the most common value. Range: the largest minus the smallest.
Worked example
A hydrograph shows peak rainfall at 06:00 and peak discharge at 14:00. Find the lag time, and say what a shorter lag time would mean.
- Lag time = 14:00 − 06:00 = 8 hours.
- A shorter lag time means the rain reaches the river more quickly.
- The river rises faster and higher, so flooding is more likely. This happens in urban areas and on steep, deforested slopes.
Tips and tricks
- Always quote data. "It increases" earns less than "it increases from 12 °C in January to 28 °C in July".
- Choose the graph for the data: time, categories, parts of a whole, or a relationship.
It lands in your notebook with its questions as flashcards.
Graphs and data skills: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
Which graph best shows change over time?
The line shows the trend.
Which graph shows the relationship between two variables?
A line of best fit can be added.
On a climate graph, how is rainfall usually shown?
Temperature is the line.
What is lag time on a flood hydrograph?
A short lag time means a higher flood risk.
What is the median of 4, 9, 2, 7, 5?
In order: 2, 4, 5, 7, 9. The middle value is 5.
What is an anomaly?
It should be pointed out and, if possible, explained.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 8 marks. Write your answers on paper, then check them.
Graphs and data skills
Cambridge IGCSE Geography (9–1) 0976 · 8 marks · papermunch.org
Name ______________________________ Date ______________
State the most suitable type of graph to show how the population of a city changed between 1950 and 2020, and give a reason.[2]
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A line graph, because it shows change over time.
Describe what a positive correlation on a scatter graph shows.[2]
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As one variable increases, the other also increases.
Six sites on a river have widths of 2, 3, 3, 5, 7 and 10 metres. Calculate the mean, median, mode and range.[4]
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Mean 5 m, median 4 m, mode 3 m and range 8 m.
Answers: Graphs and data skills
- 1. A line graph, because it shows change over time.
- 2. As one variable increases, the other also increases.
- 3. Mean 5 m, median 4 m, mode 3 m and range 8 m.