sampling

• what is the memory aid 


  r - random sample

  o - opportunity smoke

  v - volunteering sample

  s - systematic sample

  s - stratified sample
• how would you do a random sample


  • identify all the names of the participants e.g all the names of children in a show
  • put all the names onto identical pieces of paper into a 'hat'
  • draw names blind
  • allocate participants to conditions
• what do you get from a random sample


  • representative of the target population
  • generalised findings to the population
  • high population validity
• how do you do an opportunity sample


  • researcher approaches potential available participants
  • those who agree to take part become the sample
• what do you get from an opportunity sample


  • bias
  • not representative of the target population
  • low population validity
• how do you do a volunteer sample


  • put an advert in newspaper/ online
  • those who want to participate will approach the researcher
  • put an advert in newspaper/ online
  • those who want to participate will approach the researcher
• what do you get from a volunteer sample


  • not representative of the target population - participant variables
  • not everyone in the target population has a chance of being selected
• how do you do stratified sampling


  • identify all members of the target population
  • identify different sub groups relevant to your study
  • randomly select from each category in the same proportion that they exist in the target population
• what do you get from stratified sampling

  • representative of the target population
  • more likely than random sampling
  • identified sub groups all people are represented
• how do you do systematic sampling 


  • the target population are put into a list and then every nth person is chosen
  • divide population size by sample size