Sampling techniques

• Opportunity sampling:

  • A sample of participants produced by selecting people who are most easily available at the time of the study.
• Random sampling:

  • A sample of participants produced by using a random technique such that every member of the target population has an equal chance of being selected.
  • ie placing all names of a targeted population in a hat and drawing out the required number.
• Self-selected sampling:

  • A sample of participants produced by asking for volunteers.
  • For example, advertisement on a newspaper or on a noticeboard.
• Snowball sampling:

  • Relies on referrals from initial participants to generate additional participants.
• Positive and negative of opportunity sampling:

  
  

  + Takes less time to locate your sample. You just use the participants you can find.

  • Biased because the sample is drawn from a small part of the target population.
• Positive and negative of Random sampling:

  + Unbiased. All members of the target population have an equal chance of selection.

  • Takes more time and effort than other methods. you need to obtain a list of all target members of the population. Then identify the sample and ask the participants for consent to take part.
• Positive and negative of self selected sampling:

  + Convenient way to find willing participants. Researchers need committed participants for time consuming studies.

  + Participants less likely to drop out as they volunteered.

  • Sample is biased because volunteer participants are more likely to be highly motivated and/or with extra time in their hands than the population in general. (= volunteer bias)
• Positive and negative of snowball sampling:

  + Enables a researcher to locate groups of people who are difficult to access, such as people who go bowling or drug addicts.

  • Sample is not likely to be a good cross section from the population because it is friends of friends.