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Principles of Research and Application of Research Methods

Participants and Sampling: systematic sampling, stratified sampling and quota sampling

  • 3 things to know
  • AS Unit 2

Overview

Recall questions on systematic sampling, main weakness of systematic sampling and stratified sampling.

What you need to know

Answer each one before you reveal it.

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Key term

A researcher has a sampling frame of 400 names and wants a systematic sample of 20. What is the sampling interval?

Evaluation

What is the main weakness of systematic sampling?

Key term

Why is stratified sampling usually the most representative technique?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is systematic sampling?

    Model answer

    Selecting every nth member of the sampling frame, ideally beginning from a randomly chosen starting point.

  2. 2

    A researcher has a sampling frame of 400 names and wants a systematic sample of 20. What is the sampling interval?

    Model answer

    The interval is 20, so every twentieth name on the list is selected.

  3. 3

    What is the main weakness of systematic sampling?

    Model answer

    If the list contains a repeating pattern that coincides with the interval, the sample selected will be systematically biased.

  4. 4

    What is stratified sampling?

    Model answer

    Dividing the target population into subgroups, or strata, and selecting participants randomly from each in proportion to that subgroup's size in the population.

  5. 5

    Why is stratified sampling usually the most representative technique?

    Model answer

    Every important subgroup appears in the sample in the same proportion as in the population, and members within each stratum are chosen without researcher bias.

  6. 6

    A population of 500 contains 300 women. How many women and men would a representative stratified sample of 50 contain?

    Model answer

    It would contain 30 women and 20 men.

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