Edexcel GCSE Mathematics Statistics: a complete overview of sampling, averages, charts and scatter graphs

What this content demands

Statistics is the data-handling side of the course. Edexcel tests how you collect data fairly, summarise it with averages and spread, present it with the right diagram, and interpret relationships between variables. Many questions reward clear explanation in context, not just calculation, so practise writing conclusions.

This guide walks through the four areas and ties together the matching dot-point pages, each of which has its own practice questions.

Sampling and data

A sample stands in for a population, so it must be representative and large enough; biased samples over-represent some groups, and random sampling reduces bias. Data is qualitative (words) or quantitative (numbers), and quantitative data is discrete (counted) or continuous (measured). Good questionnaires are neutral, clear, and have non-overlapping response options.

Averages and spread

The mean (total over count), median (middle when ordered), mode (most common) and range (max minus min) each summarise data differently. From a frequency table, the mean is $\dfrac{\sum fx}{\sum f}$. For grouped data, use midpoints to estimate the mean and identify the modal class. Compare distributions with an average and the range, in context.

Statistical charts and graphs

Bar charts and pie charts show categorical data, with a pie chart angle being $\dfrac{\text{frequency}}{\text{total}} \times 360^\circ$. Frequency polygons join class midpoints. Cumulative frequency graphs (Higher) give the median and quartiles, read at a half, a quarter and three quarters of the total. Box plots display the five-number summary and make comparing spread easy.

Scatter graphs and correlation

A scatter graph shows whether two variables are related: positive correlation (rising), negative (falling) or none. A line of best fit estimates one variable from the other within the data range (interpolation). Extrapolating beyond the data is unreliable, and correlation does not prove causation.

Check your knowledge

A mix of statistics questions across the four areas. Attempt them under timed conditions, then check against the solutions.

1. Find the mean of $4, 7, 8, 5, 6$. (2 marks)
2. Find the median of $9, 3, 5, 8, 2, 7$. (2 marks)
3. Find the range of $14, 9, 21, 6, 18$. (1 mark)
4. In a survey of $72$ people, $24$ chose pizza. Find the pie chart angle for pizza. (2 marks)
5. State the type of data: the number of cars in a car park. (1 mark)
6. Give one reason a survey of only your friends might be biased. (1 mark)
7. A data set has lower quartile $12$ and upper quartile $20$. Find the interquartile range. (1 mark)
8. A scatter graph of revision hours against marks shows points rising to the right. Describe the correlation in context. (2 marks)