Sampling

• Sampling methods


  • Probability samples
  • Non-probability samples
• Simple random sampling


  Everyone in population has equal chance of being sampled
• Stratified sampling


  • Population is first divided into groups (e.g., gender, ethnicity, age)
  • Within each group, a probability sample (often a simple random sample) is selected
• Quota sampling


  • Same idea as stratified without the simple random sample
  • picking carefully the sampling
• Convenience sampling


  • Whoever is easiest to get
• Consecutive sampling


  • Keep using convenience sample
• Snowball sampling


  • Participants in your study recruit others that they know
• Volunteer sampling


  • Whoever volunteers
• The method that minimizes risk to participants should be the preferred choice
• Acceptance bias


  Occurs when there is something systematic about the people that choose to be in your experiment
• Rejection bias


  Occurs when there is something systematic about people that don't participate in your study
• Ceiling effect


  Occurs when you are measuring something (DV) that is already topped-out
• Floor effect


  Occurs when you are measuring something (DV) that is already bottomed-out