Sampling Methods: Target Populations & Samples (AQA GCSE Psychology): Revision Note

The target population is the group that the researcher is interested in studying, from which a smaller sample is selected

A sample is a subset of the target population which aims to be representative of that population

• A sample consists of the participants who will actually take part in the research

• The sample is drawn from the target population relevant to the research topic, e.g.:

  • Teen mothers

  • Office workers in Scotland

  • People aged 60–85 who have dementia

A target population has distinct characteristics of particular interest to the researcher

• Once it has been identified, the researcher draws a sample from it

The target population doesn't always need to be narrow or highly specific; how broad or specific it is depends on what the research question requires, e.g.:

• Research into the effect of loud music on concentration might use the general public as its target population, since concentration is relevant to everyone

• Research into the duration of STM doesn't need a narrow target population, since STM duration is similar across most adults aged 18–60

Researchers use different sampling methods to select their sample from the target population

Once the research process is over, the researcher analyses their findings and draws conclusions

One issue with a small, limited or highly specific sample is that it is very difficult to generalise the findings beyond the scope of that sample, e.g.:

• A sample of 25 office workers from Glasgow does not represent office workers in other parts of Scotland or the UK; the findings can only be generalised to other office workers of a similar age from Glasgow

• To make the sample more representative, the researcher could use stratified sampling to include office workers from different parts of the UK in proportion to the population

Data from a small sample is less robust: individual participants' scores carry more weight, and the results are less likely to reach statistical significance, meaning a real effect could be missed

• Larger samples are more robust and produce more reliable data

There are several reasons small samples are used in psychological research:

• Running research is expensive, so it may only be possible to conduct a small-scale study

• It may be difficult to find enough participants, particularly if the research requires a very specific sample

• The researcher may have limited time, so they use whoever is most convenient, e.g. university students

• Some qualitative research, such as case studies and interviews, tends to use small samples

A sample whose participants share characteristics not representative of the target population as a whole is a biased sample, and its results are difficult to generalise

• e.g. all from the same town, the same age, or with similar personality traits