sampling tecniques

• sampling types

  there are 5 different types

  1. random
  2. opportunity
  3. volunteer
  4. systematic
  5. stratified
• random sampling


  A random sample is a sophisticated form of sampling in which all members of the target population have an equal chance of being selected. 
• random sampling strengths

  • A random sample is a sophisticated form of sampling in which all members of the target population have an equal chance of being selected. 
  • How can a rese
• random sampling limitation

  • Impractical: random sampling is difficult to achieve, not all members may be available or wish to take part
  • Not representative: unbiased selection does not guarantee an unbiased sample. For example only females may be selected which is both unrepresentative and not generalisable 
• opportuniuty sampling 


  • Involves selecting p’s who are available and willing to take part. For example- asking people in the street who are passing.
• opportunity sampling strengths

  • Relatively easy to create as they are people who are readily available 
  • Usually used for natural experiments as the researcher has no control over who is studied
• opportunity sampling limitations

  • Unrepresentative: likely to be biased as it would not include p’s from different areas/backgrounds
  • Self-selection: p’s have the option to decline to take part and the sampling technique may turn into a self-selected sample
• systemtaic sampling 


  • Involves taking every nth person from a list to create a sample.
  • This involves calculating the size of the population, then assessing what size the sample needs to be to work out what the sampling interval is.
• systematic sampling strengths

  • Unbiased selection: increases the chances of getting a representative sample which will also be generalisable
• systemtic sampling limitation

  • Periodic traits: this process can interact with a hidden periodic trait, if this happens the sample is neither representative or random. 
• strtatififed sampling

  • A stratified sample is a sophisticated form of sampling in which the arrangement of the sample reflects the proportions of people in certain sub-groups (strata) within the target population or the wider population. 
  • To carry out a stratified sample the researcher first identifies the different strata (age, gender, social class etc) that make up the population, then the proportions needed for the sample to be representative are worked out.
  • Finally, the participants that make up each strata are selected using random sampling.
• stratified sampling strengths

  • Representative: selection occurs from representative sub-groups
  • Unbiased: random sampling is performed upon the sub-group of a population
• startified sampling limitations

  • They require a detailed knowledge of the population characteristics which may not be available
  • The dividing of a population into stratums and then randomly selecting from each can be time-consuming 
• volunteer sampling 


  • Where p’s select themselves.
  • This could be done through advertisements that are places in newspapers or noticeboards and p’s come to the researcher.
• volunteer sampling limitation

  • Unrepresentative: the sample will be biased as volunteers tend to be a certain ‘type of person. 
  • Demand characteristics: volunteers are eager to please- p’s may give the answer they think is required. 
• volunteer sampling strengths

  • Participants are willing: they are likely to engage more than people stopped in the street.