Sampling methods critique

A question is this type if and only if it asks to identify problems with proposed sampling methods, explain why they are biased, or suggest appropriate sampling methods.

2 questions

OCR S2 2009 June Q4
4 A survey is to be carried out to draw conclusions about the proportion \(p\) of residents of a town who support the building of a new supermarket. It is proposed to carry out the survey by interviewing a large number of people in the high street of the town, which attracts a large number of tourists.
  1. Give two different reasons why this proposed method is inappropriate.
  2. Suggest a good method of carrying out the survey.
  3. State two statistical properties of your survey method that would enable reliable conclusions about \(p\) to be drawn.
OCR MEI Paper 2 Specimen Q10
10 A researcher wants to find out how many adults in a large town use the internet at least once a week. The researcher has formulated a suitable question to ask. For each of the following methods of taking a sample of the adults in the town, give a reason why the method may be biased. Method A: Ask people walking along a particular street between 9 am and 5 pm on one Monday.
Method B: Put the question through every letter box in the town and ask people to send back answers.
Method C: Put the question on the local council website for people to answer online.