GCSE · Sampling

Bias & sampling methodsExam-style questions

What bias really is — a method that systematically leaves people out, so a bigger sample never fixes it — how to name who is missing, the strengths and weaknesses of random, systematic, stratified and convenience sampling, and how to criticise and rewrite a questionnaire.

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11 questions · GCSE (Higher) level · mark scheme and worked solution on each · no sign-up to try

DifficultyAllLevel 1Level 2Level 3Level 4Level 5
  1. 1
    A town council wants to find out what the town's residents think about a plan to build a new car park in the town centre. A researcher stands outside the town's largest supermarket between 10 am and midday on a Wednesday and asks 100 shoppers for their views.

    (a) Give two reasons why this sample may not represent the views of all the town's residents.

    (b) The researcher says: "I will ask 500 shoppers instead of 100. Then the sample will represent the town." Explain why he is wrong.

    (c) Describe a better method the council could use to choose its sample.
    Level 4 · 4 marksTry it
  2. 2
    A school council is writing a questionnaire about the new school dinners. This is one question from it.

    Most students think the new school dinners are excellent. Don't you agree?
    • Yes
    • No
    (a) Write down two criticisms of this question.

    (b) Rewrite the question so that it is suitable for the questionnaire. You must include suitable response boxes.
    Level 4 · 4 marksTry it