research methods - sampling

• Systematic sampling


  • Conscientious bias
  • One chance to be not representative
  • More time consuming than random
• Systematic sampling


  Within a sampling frame, selecting from every nth term to carry out the sample
• Participant


  Internal validity
• External validity


  Generalisable to the population
• Stratified sampling


  • Representative, unbiased
  • Time consuming, expensive
• Stratified sampling


  Sampling frame being divided based on a characteristic into a smaller group (e.g. age, gender, socioeconomic class)
• Volunteer sampling


  • Ethical
  • Less time consuming
  • May not be representative
• Volunteer sampling


  • Participants come to you
• Participants come to you and choose to take part

  Confounding by participant
• Opportunity sampling


  • Choosing people who are cheap and available
  • Less time consuming, efficient
  • May not be representative
  • Can't generalise
• Extraneous variable is a confound
• Biased from who's available
• Can't generalise it