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
    Tom wants to find out how often people in his town go swimming. He asks people leaving the swimming pool. Explain why this sample is biased.
    Level 1 · 1 markTry it
  2. 2
    A council wants to find out what people in the town think about a new bus route.

    The council asks 3030 people waiting at the bus station one Monday morning.
    (a) Give one reason why this sample may be biased. (1 mark)
    (b) Suggest one way the council could improve the sample. (1 mark)
    Level 1 · 2 marksTry it
  3. 3
    Priya wants to find out how much time students at her school spend on homework each week. She asks the 20 students in her own maths class.

    (a) Write down the type of sample Priya has taken.

    (b) Explain why her sample may be biased.
    Level 2 · 2 marksTry it
  4. 4
    Describe how to choose a random sample of 2020 students from a year group of 200200.
    Level 2 · 2 marksTry it
  5. 5
    A gym is writing a questionnaire for its members. This is one question from it.

    How many hours do you exercise?
    • 0 – 2
    • 2 – 4
    • 4 – 6
    (a) Write down two things that are wrong with this question.

    (b) Write an improved version of the question. You must include suitable response boxes.
    Level 3 · 4 marksTry it

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