Sampling

• Opportunity


  • consists of taking people who are readily available at the time the study is carried out

  S

  • really easy and quick compared to random and stratified

  W

  • limited to whoever is available at the time and may not be representative
  • may be biased
• Volunteer


  • consists of Ps becoming part of a study because they volunteer

  S

  • Ps are willing to be involved and are likely to be more motivated

  W

  • more likely to please researcher
  • may not be representative of pop
• Stratified


  • classifying pop into categories and choosing a sample that consists of Ps from eah category in the same proportions as the pop

  S-

  • ensures good representation from each group

  W-

  • detailed knowledge of pop characteristics which may not be available and time consuming to find out
• Systematic


  • taking every nth person to create a sample

  S-

  • no bias

  W-

  • hidden periodic trait for every nth person
  • may not want to take part, meaning you have a volunteer sample
• Random


  • identify everyone in target pop
  • select n.o. of Ps needed
  • then use a hat/random number generator to choose

  S-

  • likely to be unbiased
  • fairly representative
  • generalisable

  W-

  • time consuming to obtain a list of every member of target population