Sampling Methods

• Sample

  A selection taken from the target population which must be representative in order to be able to generalise findings
• Random sampling

  Every member of the population has an equal chance of being selected
• :) Random sampling (2)

  :) Unbiased (for a large sample)

  :) No researcher bias
• :( Random sampling

  :( Time consuming to list everyone

  :( May not be representative
• Opportunity sample

  Selecting people who are available at the time
• :) Opportunity

  :) Quick, convenient, economical

  :) Ethical - participants consent
• :( Opportunity

  :( May not be representative

  :( Researcher bias
• Volunteer

  Individuals who have chosen to be in the study
• :) Volunteer

  :) Convenient

  :) Ethical - consent

  :) Practical and easy
• :( Volunteer

  :( May be unrepresentative

  :( Participant bias
• Systematic

  Chosen in a systematic way e.g. every nth person (regular intervals)
• :) Systematic

  :) Generally representative

  :) Unbiased
• :( Systematic

  :( Time consuming and takes effort

  :( May not always be representative
• Stratified

  Dividing population into relevant subcategories and selecting members in proportion that they occur in the population
• :) Stratified

  :) Representative

  :) Unbiased
• :( Stratified

  :( Time consuming as calculations must be made