Sampling

• Sample and target population


  When conducting research, psychologists select a sample, which is a small group of participants. A target population. which is the group of people the researchers are interested in and to whom they wish to generalize their findings.
• Generalizability & representatives


  • Aim to generalize findings from their experiment to the target population.
  • Ensure the sample is representative of the target population.
• How many participants should be in a sample?


  • Varies
  • Large enough to be representative of the target population.
  • Too many participants makes research expensive and time-consuming.
  • If research has important implication, the sample size should be larger.
  • If the effect being studied is likely to be small, a larger sample size required.
  • It also depends on the technique.
• Opportunity sampling (OS)

  Selecting people who are most easily available at the time of the study and are willing to participate,
• Strengths and weaknesses of OS


  + easiest, inexpensive, less time-consuming.

  _ people gathering in the same places will tend to be similar in some way.
• Self-selected sampling (SSS)

  Asking for volunteers.
• Strengths and weaknesses of SSS


  + researchers need committed participants for time-consuming studies.

  + less likely to drop out as they volunteered.

  _ more highly motivated, more helpful/curious and/or with extra time on their hands.

  _ volunteer bias.
• Snowball sampling (SS)


  Referrals from initial participants to generate additional participants.