- The Headteacher of a school is thinking about making changes to the school day. She wants to take a sample of 60 students so that she can find out what the students think about the proposed changes.
The names of the 1200 students of the school are listed alphabetically.
- Explain how the Headteacher could take a systematic sample of 60 students.
- Explain why systematic sampling is likely to be quicker than simple random sampling in this situation.
- With reference to this situation,
- explain why systematic sampling may introduce bias compared to simple random sampling
- give an example of the bias that may occur when using this alphabetical list
When the Headteacher completes the systematic sample of size 60 she finds that 6 students were to be selected from Year 9.
The Head of Mathematics suggests that a stratified sample of size 60 would be a more appropriate method.
There were 200 students in Year 9.- Explain why this suggests that a stratified sample of size 60 may be better than the systematic sample taken by the Headteacher.