Sampling methods

• What is a target population?

  A group of people who are the focus of the researcher's interest, from which the sample is drawn
• What is a sample?

  • A group of people taken from target population who participate in research
  • Sample is assumed to be representative of target population
• What is generalisability?

  The extent to which researchers can apply their findings to the target population
• What are the two types of sample bias?

  • Gender bias
  • Cultural bias
• What are the 5 types of sampling?

  • Random
  • Systematic
  • Stratified
  • Opportunity
  • Volunteer
• What is random sampling?

  All members of the target population have an equal chance of being selected
• What is systematic sampling?

  Every nth element of the target population is selected to be in the sample
• What is stratified sampling?

  Target population is divided into distinct subgroups and a random sample is taken from each group in proportion to its size.
• What is opportunity sampling?

  Selecting anyone who is willing and available
• What is volunteer sampling?

  Participants volunteer themselves to participate
• Opportunity sampling evaluation

  • +Not time consuming
  • -Sample may not be representative of population
  • -Investigator bias
• Random sampling evaluation

  • +Unbiased
  • -Time consuming
• Stratified sampling evaluation

  • +More representative of the population
  • -Time consuming
• Systematic sampling evaluation

  • +unbiased
  • -not truly unbiased unless researcher selects first person randomly
• Volunteer sampling evaluation

  • +Easy to collect
  • -Volunteer bias