EnglandGeographySyllabus dot point

How do geographers use numbers and statistics to analyse data?

Numerical and statistical skills: calculating and interpreting measures of central tendency (mean, median, mode), measures of spread (range, interquartile range), percentages and percentage change, and describing relationships in data including the line of best fit.

A focused answer to OCR GCSE Geography B (J384) numerical and statistical skills, covering mean, median and mode, range and interquartile range, percentages and percentage change, and describing relationships including the line of best fit.

Generated by Claude Opus 4.811 min answerUpdated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this dot point is asking
Measures of central tendency
Measures of spread
Percentages and percentage change
Describing relationships and the line of best fit
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What this dot point is asking

This is OCR GCSE Geography B (J384) numerical and statistical skills, assessed across all three components and tested directly in Component 3, Geographical Exploration, and in fieldwork analysis. OCR expects you to calculate and interpret measures of central tendency (mean, median, mode), measures of spread (range, interquartile range), percentages and percentage change, and to describe relationships in data, including using a line of best fit on a scatter graph.

Measures of central tendency

These give a single "typical" value for a set of data.

For example, for the rainfall totals $20, 25, 25, 30, 50$ mm: the mean is $\frac{20+25+25+30+50}{5} = \frac{150}{5} = 30$ mm, the median is the middle value $25$ mm, and the mode is $25$ mm (the most common).

Measures of spread

These show how varied or clustered the data are.

Percentages and percentage change

Percentages compare a part with a whole, and percentage change measures growth or decline.

A percentage is a proportion out of 100: $\text{percentage} = \frac{\text{part}}{\text{whole}} \times 100$ .
Percentage change measures how much a value has risen or fallen: $\text{percentage change} = \frac{\text{new value} - \text{original value}}{\text{original value}} \times 100$ .

For example, if a city's population rose from $4$ million to $5$ million, the percentage change is $\frac{5 - 4}{4} \times 100 = 25\%$ (a 25 percent increase).

Describing relationships and the line of best fit

A scatter graph plots two variables against each other to reveal a relationship (correlation).

A line of best fit is a straight line drawn through the middle of the points, with roughly equal numbers above and below, to show the overall trend.
A positive correlation (the line slopes up) means that as one variable increases, so does the other; a negative correlation (the line slopes down) means that as one increases, the other decreases; no correlation means the points are scattered with no clear pattern.
Anomalies are points that lie far from the line and do not fit the trend.

Worked example: calculating the interquartile range

Take "Calculate the interquartile range of these ordered values: 4, 6, 8, 10, 14, 18, 22, 26. [3 marks]". Work through it.

step 1: Confirm the data are ordered

Check the eight values are in order from smallest to largest: $4, 6, 8, 10, 14, 18, 22, 26$ .

step 2: Find the lower quartile

Split into the lower half ( $4, 6, 8, 10$ ); the lower quartile $Q_1$ is the median of this half: $\frac{6 + 8}{2} = 7$ .

step 3: Find the upper quartile

Split into the upper half ( $14, 18, 22, 26$ ); the upper quartile $Q_3$ is the median of this half: $\frac{18 + 22}{2} = 20$ .

step 4: Calculate and interpret

Calculate $\mathrm{IQR} = Q_3 - Q_1 = 20 - 7 = 13$ . State that this shows the spread of the middle 50 percent of the data. The marks come from the correct quartiles and the subtraction.

Try this

Q1. Calculate the mean of these pebble lengths (cm): 3, 5, 5, 7. [2 marks]

Cue. $\frac{3 + 5 + 5 + 7}{4} = \frac{20}{4} = 5$ cm.

Q2. A figure falls from 80 to 60. Calculate the percentage change. [2 marks]

Cue. $\frac{60 - 80}{80} \times 100 = -25\%$ (a 25 percent decrease).

Exam-style practice questions

Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

OCR 20193 marksUsing the data, calculate the median and the range of the river velocity readings. (Component 3)

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A 3-mark calculation question assessing AO4 (skills). Markers reward the correct method and answer, with working.

Method: to find the median, put the values in order from smallest to largest and find the middle one (if there are two middle values, take their mean). To find the range, subtract the smallest value from the largest. For example, for the readings 0.2, 0.3, 0.5, 0.6, 0.8 m/s, the median is the middle value $0.5$ m/s and the range is $0.8 - 0.2 = 0.6$ m/s. Top answers show the ordered list and the subtraction, and give the units. A common error is to forget to order the data before finding the median.

OCR 20214 marksUsing the data in the table, calculate the interquartile range and explain what it shows. (Component 3)

Show worked answer →

A 4-mark calculation-and-interpretation question assessing AO4. Markers reward the method, the value and the interpretation.

Method: order the data, then find the lower quartile (the median of the lower half, $Q_1$ ) and the upper quartile (the median of the upper half, $Q_3$ ). The interquartile range is $\mathrm{IQR} = Q_3 - Q_1$ . For example, if $Q_1 = 12$ and $Q_3 = 28$ , then $\mathrm{IQR} = 28 - 12 = 16$ . Interpretation: the IQR measures the spread of the middle 50 percent of the data, ignoring extreme values, so a small IQR means the data are closely clustered and a large IQR means they are widely spread. Top answers give the working, the value with units, and a clear interpretation of what the spread shows.

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Sources & how we know this

OCR GCSE (9-1) Geography B (J384) specification — OCR (2016)