Sampling

• Random sampling


  every member of the target population has same chance of being chosen for the sample

  Advantages:

  - free from researcher bias

  Disadvantages:

  - difficult to obtain

  - could lack population validity
• Systematic sampling


  where you have a list of the target population and you choose members through a sequence

  Advantages:

  - free from researcher bias

  Disadvantages:

  - may still not be representative
• Stratified sampling


  list is made of each variable - may effect research

  work out % of each variable

  sample then contains the same proportion of people

  Advantages:

  - produce a representative sample

  Disadvantages:

  - not perfect as it's hard to identify all the different strata

  - time consuming
• Opportunity sampling


  the researchers uses ppts that are willing and available

  Advantages:

  - easy to obtain

  Disadvantages:

  - very biased

  - lacks population validity
• Volunteer sampling


  ppts choose themselves -> answering an advert in a newspaper, relying on a postal questionnaire

  Advantages:

  - easy to obtain

  Disadvantages:

  - lacks population validity