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Geographical Skills

Sampling and sources of error

  • 3 things to know
  • All three components

Overview

Random sampling, systematic sampling and stratified sampling.

What you need to know

Answer each one before you reveal it.

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Key term

Why is sampling used in geographical fieldwork?

Key term

Define random sampling.

Evaluation

State one advantage and one disadvantage of random sampling.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Why is sampling used in geographical fieldwork?

    Model answer

    Measuring an entire population is usually impossible within the time and resources available. A sample allows a valid estimate from a manageable number of observations.

  2. 2

    Define random sampling.

    Model answer

    Random sampling gives every member of the population an equal chance of selection. Points are chosen using random numbers rather than judgement.

  3. 3

    State one advantage and one disadvantage of random sampling.

    Model answer

    Random sampling avoids bias and allows statistical testing. Small subgroups may be missed entirely by chance.

  4. 4

    Define systematic sampling.

    Model answer

    Systematic sampling selects at a regular interval, such as every tenth house or every 50 metres. The pattern is decided before fieldwork begins.

  5. 5

    State one advantage and one disadvantage of systematic sampling.

    Model answer

    Systematic sampling is quick to organise and gives even coverage. A regular interval can coincide with a pattern in the landscape and hide variation.

  6. 6

    Define stratified sampling.

    Model answer

    Stratified sampling divides the population into subgroups and samples each in proportion to its size. The method ensures every subgroup is represented.

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