GCSE-ready- Home
- Lessons
- GCSE & IGCSE Geography A
- Statistics: averages, range and percentage change
Statistics: averages, range and percentage change
🎬 The doodle video for this lesson is coming soon. Subscribe on YouTube to see it first.
Geography exams always include calculations. Most use a few simple techniques.
Averages
Mean: add the values and divide by how many there are.
Median: the middle value when the data are in order. It is not affected much by extreme values.
Mode: the most common value.
Range: highest − lowest. It shows how spread out the data are.
Median: the middle value when the data are in order. It is not affected much by extreme values.
Mode: the most common value.
Range: highest − lowest. It shows how spread out the data are.
Interquartile range
Put the data in order. The lower quartile is the median of the lower half; the upper quartile is the median of the upper half.
Interquartile range (IQR) = upper quartile − lower quartile.
The IQR shows the spread of the middle half of the data and ignores extreme values.
Interquartile range (IQR) = upper quartile − lower quartile.
The IQR shows the spread of the middle half of the data and ignores extreme values.
Percentages
Percentage = partwhole × 100
Percentage change = (new − old) ÷ old × 100
A negative answer is a percentage decrease.
You may also need rates, such as population per km2 (population density = population ÷ area).
Percentage change = (new − old) ÷ old × 100
A negative answer is a percentage decrease.
You may also need rates, such as population per km2 (population density = population ÷ area).
A town's population grew from 40,000 to 46,000. Find the percentage change.
- Change = 46,000 − 40,000 = 6,000
- Percentage change = 6,000 ÷ 40,000 × 100
Answer: 15% increase
Mean = total ÷ number; median = middle value; mode = most common; range = highest − lowest. IQR = upper quartile − lower quartile. Percentage change = (new − old) ÷ old × 100. Population density = population ÷ area.
Check you have got it
Answer 7 quick questions with instant marking. If you get one wrong, GCSE-ready shows you why and gives you another go. It is free, and you do not need an account.