Sampling

• What is opportunity sampling


  People who are simply most available
• Strength and limitation of opportunity sampling

  strength: Quick method

  limitation : inevitably biased- unrepresentative so cannot be generalised
• What is Volunteer sampling


  Participant selects themselves
• Strength and limitation of volunteer sampling

  strength: ppts are willing

  limitation: likely to be a biased sample- limited generalisation
• What is a random sample

  Every person in the target population has an equal chance of being selected
• Strength and limitation of random sample 


  strength: potentially unbiased-researcher has no influence over ppts selected

  limitation: representation not guaranteed
• What is systematic sampling

  Participants are selected using a set pattern
• Strength and limitation of systematic sampling


  strength: unbiased-objective method

  limitation: time and effort
• What is stratified sampling 


  Ppts are selected according to their frequency in the target population
• Strength and limitation of stratified sampling

  strength: representative method

  limitation: not perfect- complete representation isnt possible
• How is stratified sampling carried out

  • Strata are identified
  • relative percentages of strata in population are reflected in the sample