Pearson Edexcel · GCSE · Psychology

    Course version: 1PS0 · Version from Sept 2017

    Methods of sampling, including strengths and weaknesses of each sampling…

    Full specification wording

    Designing psychological research: 11.1.5 Methods of sampling, including strengths and weaknesses of each sampling method: a. understand target population samples b. understand random sampling c. stratified sampling d. volunteer sampling e. opportunity sampling

    A target population is the specific group a researcher wants to study.

    Checked against the Pearson Edexcel 1PS0 specification (opens in a new tab) on .

    • Point 5 of 17
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    A target population is the specific group a researcher wants to study. Since testing everyone is rarely possible, researchers select a sample. Random sampling gives every member an equal chance of selection, reducing bias but requiring a full list of the population. Stratified sampling divides the population into subgroups and selects participants proportionally, ensuring high representativeness, though it is time-consuming. Volunteer sampling relies on participants putting themselves forward; it is ethical and easy, but often suffers from volunteer bias. Opportunity sampling selects anyone available at the time, making it quick and convenient, but highly unrepresentative of the wider target population.

    What earns the marks

    • Defines target population as the entire group of interest from which a sample is drawn.
    • Evaluates random sampling: strength is lack of researcher bias; weakness is the difficulty of obtaining a complete population list.
    • Evaluates stratified sampling: strength is proportional representation; weakness is the complexity and time required to calculate strata.
    • Evaluates volunteer sampling: strength is participant willingness; weakness is a biased sample of highly motivated individuals.
    • Evaluates opportunity sampling: strength is convenience and speed; weakness is high vulnerability to researcher bias and unrepresentativeness.

    Common mistakes and how to put them right

    • Confusing random sampling with opportunity sampling.

      Put it right: Random sampling requires a systematic method where everyone has an equal chance, whereas opportunity sampling just takes whoever is available.

    • Stating that stratified sampling is completely free from bias.

      Put it right: Acknowledge that while it is highly representative, bias can still occur if the strata are not defined accurately.

    • Assuming volunteer sampling is always representative.

      Put it right: Recognise that volunteers often share specific traits, such as having more free time, which limits generalisability.

    Exam tips

    • When evaluating a sampling method, always link its strength or weakness back to how it affects the generalisability of the findings.
    • Use the specific scenario provided in the exam to justify why a particular sampling method would be the most appropriate choice.
    • Clearly distinguish between the target population, which is the whole group, and the sample, which is the participants actually tested.

    Try the lesson

    The start of the Designing psychological research: 11.1.5 Methods of sampling, including strengths and weaknesses of each sampling method: a. understand target population samples b. understand random sampling c. stratified sampling d. volunteer sampling e. opportunity sampling lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which of the following is the correct definition of a random sample?

    Listen

    A target population is the specific group a researcher wants to study. Since testing everyone is rarely possible, researchers select a sample. Random sampling gives every member an equal chance of selection, reducing bias but requiring a full list of the population. Stratified sampling divides the population into subgroups and selects participants proportionally, ensuring high representativeness, though it is time-consuming. Volunteer sampling relies on participants putting themselves forward; it is ethical and easy, but often suffers from volunteer bias. Opportunity sampling selects anyone available at the time, making it quick and convenient, but highly unrepresentative of the wider target population. A strong answer earns marks for these points. Defines target population as the entire group of interest from which a sample is drawn. Evaluates random sampling: strength is lack of researcher bias; weakness is the difficulty of obtaining a complete population list. Evaluates stratified sampling: strength is proportional representation; weakness is the complexity and time required to calculate strata. Evaluates volunteer sampling: strength is participant willingness; weakness is a biased sample of highly motivated individuals. A common slip: Confusing random sampling with opportunity sampling. Instead, random sampling requires a systematic method where everyone has an equal chance, whereas opportunity sampling just takes whoever is available. Exam tip: When evaluating a sampling method, always link its strength or weakness back to how it affects the generalisability of the findings.

    See it

    A top-down flowchart. At the top, a node labelled Target population leads down to a node labelled Sample selected. From Sample selected, four branches lead to the four sampling methods: Random sampling, Stratified sampling, Volunteer sampling and Opportunity sampling. Each method then splits into two nodes giving its strength and its weakness. Random sampling leads to Strength: lack of researcher bias and Weakness: difficulty obtaining complete population list. Stratified sampling leads to Strength: proportional representation and Weakness: complex and time-consuming strata. Volunteer sampling leads to Strength: participant willingness and Weakness: biased sample of motivated individuals. Opportunity sampling leads to Strength: convenience and speed and Weakness: researcher bias and unrepresentativeness.
    Shows how a sample is drawn from a target population using four sampling methods, each with its main strength and weakness.

    Key words

    Say what each word means before you turn the card.

    Target population

    Try answering aloud or in your head before turning the card.

    Random sampling

    Try answering aloud or in your head before turning the card.

    Stratified sampling

    Try answering aloud or in your head before turning the card.

    Volunteer sampling

    Try answering aloud or in your head before turning the card.

    See every definition
    Target population
    The specific group a researcher wants to study, from which a sample is drawn.
    Random sampling
    A method that gives every member of the population an equal chance of selection, reducing bias but requiring a full list of the population.
    Stratified sampling
    Divides the population into subgroups and selects participants proportionally, ensuring high representativeness, though it is time-consuming.
    Volunteer sampling
    Relies on participants putting themselves forward; it is ethical and easy, but often suffers from volunteer bias.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. At the top, a node labelled Target population leads down to a node labelled Sample selected. From Sample selected, four branches lead to the four sampling methods: Random sampling, Stratified sampling, Volunteer sampling and Opportunity sampling. Each method then splits into two nodes giving its strength and its weakness. Random sampling leads to Strength: lack of researcher bias and Weakness: difficulty obtaining complete population list. Stratified sampling leads to Strength: proportional representation and Weakness: complex and time-consuming strata. Volunteer sampling leads to Strength: participant willingness and Weakness: biased sample of motivated individuals. Opportunity sampling leads to Strength: convenience and speed and Weakness: researcher bias and unrepresentativeness.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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