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AQA GCSE · Question 05.2 · Data Collection and Sampling Methods
Give two other reasons why this sample of students might not be representative of all secondary school students in the city.
Give two other reasons why this sample of students might not be representative of all secondary school students in the city.
How to approach this question
1. Think about the details of the method: "first 500 students they meet".
2. Consider who might be included or excluded by this method.
3. Reason 1: The "first 500" is a non-random method called convenience sampling. This group might share characteristics (e.g., all Year 7s arriving for an assembly) that make them different from the general school population.
4. Reason 2: The timing of the survey could introduce bias. Students arriving at a certain time might be from the same area (e.g., off the same bus) or in the same year group.
5. Reason 3: Not all students might be available or willing to be surveyed (non-response bias).
6. Write down two distinct reasons.
Full Answer
1. **Convenience Sampling**: The researcher surveyed the "first 500 students they meet". This is a convenience sample and is likely to be biased. For example, they might all be from a particular year group arriving at the same time, or students who are more outgoing and willing to participate.
2. **Time of Day**: The survey was conducted at a specific time. This could exclude students who arrive earlier or later, or those who are absent on that day, who may have different characteristics from those surveyed.
Even within the single school, the sampling method has flaws that could make the sample unrepresentative.
1. **Convenience Sampling**: By choosing the "first 500 students", the researcher is not giving every student an equal chance of being selected. This group might be biased. For instance, if the researcher stands by the gate in the morning, they might survey students who arrive early, who could be systematically different from those who arrive just on time or late.
2. **Non-response Bias**: Not every student approached may agree to participate. If students who refuse to participate share a common characteristic (e.g., they are shy, or they dislike the movie genre being asked about), the results will be skewed.
3. **Temporal Bias**: Surveying on one specific day means any student who is absent will be excluded. If absence is linked to factors that might also link to movie preference (e.g., socio-economic background), the sample will be biased.
Common mistakes
✗ Giving the same reason twice in different words (e.g., "It's not random" and "Not everyone has an equal chance").
✗ Repeating the answer from part (a) about it being only one school.
✗ Vague answers like "it's not fair".
Practice the full AQA GCSE Statistics Higher Tier Paper 1
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