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 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
  2. 2
    A factory employs 480 workers. They are shown on a staff list, numbered 1 to 480. A manager wants a sample of 60 workers. She chooses worker number 8, then worker number 16, then worker number 24, and so on, taking every 8th worker on the list.

    (a) Write down the name of this type of sampling.

    (b) Explain why the manager's sample is not a random sample.

    (c) Give one advantage of this method over choosing 60 workers at random from the whole list.
    Level 3 · 3 marksTry it
  3. 3
    A school has 1000 students. Three teachers each choose a sample of 50 students.
    • Mr Ahmed numbers every student on the school register from 1 to 1000 and uses a random number generator to pick 50 numbers.
    • Mrs Bell splits the students into their five year groups and picks students at random from each year group, so that each year group is represented in proportion to its size.
    • Mr Clarke asks the first 50 students to arrive at school one morning.
    (a) Write down the name of the sampling method each teacher has used.

    (b) Explain why Mr Clarke's sample is likely to be biased.
    Level 3 · 4 marksTry it