Participants and Sampling

• target population (TP)


  group of people psych want to study so findings can generalize and be representative of TP
• sampling technique


  use to help recruit participants from the TP
• Opportunity sampling


  researchers recruiting participants who happen to be around at the time they need participants; once correct number no more asked
• Self-selected/Volunteer sampling


  -researchers advertising for participants

  -frequently used in universities to recruit participants for a range of studies

  -part choose whether they want to participate or not
• Random sampling


  every participant in the TP having equal chance of being chosen

  -if TP small, numbered and chosen from hat

  -if TP large, numbered and random number generator
• Stratified sampling

  recruiting a sample that is a mini version of the TP

  -recruit from each major stratum, reflecting TP (age groups, gender, ethnicity)
• representative


  random and stratified
• strengths of representative sampling

  -researcher can generalize the TP with confidence (more representative)
• weakness of representative sampling

  -obtaining details of TP to select sample may be difficult

  -researchers cannot guarantee a representative sample
• non-representative 


  opportunity and self-selected
• strengths of non-representative

  -large number of participants can be obtained quickly and easily

  -more likely to participate if volunteered, dropout rate lower
• weaknesses of non-representative sampling

  -unlikely to gain wide variety of participants (low generalization)

  -op: one type of person; volunteer: certain type of person volunteer