Applies the four stages of the Statistical Enquiry Cycle (plan, collect, process, interpret) to exam-style questions, covering how SEC is assessed, planning investigations, evaluating methods, and writing conclusions that refer back to the original hypothesis.
Applies the four stages of the Statistical Enquiry Cycle (plan, collect, process, interpret) to exam-style questions, covering how SEC is assessed, planning investigations, evaluating methods, and writing conclusions that refer back to the original hypothesis.
For Statistical Enquiry Cycle in Practice, you must know:
Q: A student wants to investigate whether Year 11 students spend more time on homework than Year 8 students. State a suitable hypothesis and identify the population.
Q: Describe one advantage and one disadvantage of using a pilot study.
Q: A survey on exercise habits was conducted by posting questionnaires to 500 households. Only 120 were returned. Identify two sources of bias and explain how each affects the results.
Q: Explain the difference between reliability and validity in the context of a statistical investigation.
Q: A conclusion states ‘The hypothesis is supported because the mean for Group A was higher than Group B.’ How could this conclusion be improved?
✗ Writing vague conclusions without referencing data or statistics from the question ✓ Always quote specific values: ‘The median for Group A (34) was higher than Group B (27)’
✗ Confusing reliability and validity ✓ Reliability = consistency on repetition; validity = measuring what you intend to measure
✗ Forgetting to evaluate limitations when writing conclusions ✓ A strong conclusion acknowledges what the data cannot tell us, e.g. small sample size or possible bias
✗ Describing only what was done without explaining why at each SEC stage ✓ Explain reasoning: ‘Stratified sampling was used because the year groups differ in size’
A researcher investigates the hypothesis: ‘People who walk to work have lower blood pressure than people who drive to work.’ They take a random sample of 50 walkers and 50 drivers from a city and measure their blood pressure. (a) Describe the data collection stage. (b) Write a conclusion if the median blood pressure for walkers is 120/78 and for drivers is 134/86.
(a) The data collection stage involves measuring the blood pressure of 100 participants (50 walkers, 50 drivers). The sampling method is random, which reduces selection bias. Data is primary (collected firsthand) and quantitative (numerical blood pressure readings). A pilot study could test the measurement protocol. (b) The data supports the hypothesis. Walkers have a lower median systolic blood pressure (120 vs 134, a difference of 14 mmHg) and a lower median diastolic blood pressure (78 vs 86, a difference of 8 mmHg). Both groups show a clear difference that suggests walking to work is associated with lower blood pressure. However, this is an observational study so causation cannot be established — people who walk may also have other healthy habits. A larger sample and controlling for confounding variables (e.g. age, diet) would strengthen the conclusion.
AO1 (Knowledge & Understanding): Demonstrate knowledge and understanding of statistical enquiry cycle in practice, including data collection, presentation and calculation techniques relevant to Edexcel 1ST0 & AQA 8382.
AO2 (Application): Apply knowledge and understanding of statistical enquiry cycle in practice to interpret data, reason statistically and draw conclusions in context.
AO3 (Evaluation): Evaluate statistical methods and conclusions, assessing appropriateness, reliability, validity and bias through the statistical enquiry cycle.
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