A useful chart makes the data and its units clear. Bar-chart heights represent frequencies, pictogram symbols need a key, and a pie-chart sector shows a fraction of the full 360° circle. Check axis scales before comparing heights. A scatter graph shows paired measurements, with one point for each pair. An upward trend suggests positive correlation and a downward trend suggests negative correlation. A line of best fit summarises the trend rather than joining the dots. Predictions within the observed range are usually safer than predictions far outside it, and correlation alone does not prove a cause.
Learning objectives
- Read chart scales and calculate pie-chart angles.
- Describe correlation and judge predictions from scatter graphs.
Key ideas
Read the title, labels, scales and key before interpreting a chart.
Pie-chart angles show each category as a fraction of the total.
Scatter graphs plot paired values; do not join individual points with a zigzag line.
Positive correlation trends upwards; negative correlation trends downwards. Correlation does not establish cause.
Interpolation predicts within the observed range. Extrapolation predicts outside it and may be unreliable.
Worked examples
Example 1
Fifteen of forty students choose cycling. Find the cycling sector angle.
Answer
Example 2
One pictogram symbol represents eight pupils. Interpret two and a half symbols.
Answer
Question styles to prepare for
Original practice guidance aligned to the specification, not a count of past-paper appearances or a prediction. The AO labels below describe the intended practice focus, not official AQA mark allocations.
AO1 · Methods
Read or complete a chart, table or scatter graph.
AO2 · Reasoning
Describe a relationship and explain why correlation alone does not prove causation.
AO3 · Problem solving
Estimate from a line of best fit and consider whether extrapolation is reliable.
When a task asks you to explain, include a mathematical reason. When solving a problem, show how the information becomes a calculation, equation or diagram, then interpret your result.
Avoid this mistake
A trend does not prove cause and effect. Predictions beyond the observed values deserve extra caution.
Try it yourself
Attempt each question before opening its answer.
Check 1: A pictogram key says one whole symbol represents 8 pupils. How many pupils do 2.5 symbols represent?
Answer: 20 pupils
Multiply the number of symbols by the key: 2.5 × 8 = 20.
Check 2: A scatter graph shows points trending down from left to right. What type of correlation is shown?
Answer: Negative correlation
As the horizontal variable increases, the vertical variable tends to decrease.
Explain it in your own words
- Explain why a pie chart must include every category in the total.
- Draw three tiny scatter plots to show positive, negative and no correlation.
- Write a sentence explaining why a correlation cannot on its own show that one variable causes another.
Keep practising
Download the compact topic guide (PDF) · Practise this topic in Blitz · All foundation notes
Specification source
AQA Statistics specification · Assessment objectives. Checked 16 October 2026. Topic references identify related content; these notes do not cover every specification statement.