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AQA GCSE · Question 05.1 · Data Collection and Sampling Methods
BMI stands for Body Mass Index and is based on your height and mass. Louise and William have this hypothesis, "Our classmates have a lower BMI than other Year 11 students in the country." They collect height and mass data from some of their classmates, shown in the table. Give one criticism of the collected data.
BMI stands for Body Mass Index and is based on your height and mass. Louise and William have this hypothesis, "Our classmates have a lower BMI than other Year 11 students in the country." They collect height and mass data from some of their classmates, shown in the table. Give one criticism of the collected data.
How to approach this question
Look at the data collection method and the data itself. Think about the principles of good sampling. Is the sample large enough? Is it representative? Was it selected in an unbiased way? Compare the sample to the population mentioned in the hypothesis.
Full Answer
Any one of the following:
- The sample size is too small (only 10 students).
- The sample is not random / it is an opportunity sample.
- The sample may be biased (e.g., they only asked their friends).
- The sample is not representative of all their classmates, let alone all Year 11 students in the country.
- There is a repeated data point (Female, 1.38m, 51kg).
The hypothesis makes a claim about two populations: 1) "Our classmates" and 2) "other Year 11 students in the country". The data collected is a small sample of just 10 students from their class. This is a convenience sample, not a random one. Therefore, it is unlikely to be representative of their entire class, and it is certainly not sufficient to make a comparison with all Year 11 students in the country. A small, non-random sample is prone to bias and cannot be used to draw reliable conclusions about a larger population.
Common mistakes
✗ Stating a criticism that is not statistical (e.g., "they shouldn't collect personal data").\n✗ Simply saying "it is bad data" without explaining why.
Practice the full AQA GCSE Statistics Higher Tier Paper 2
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