Sampling methods

• • General population= everyone
  • Target population= selection of population to which we wish to apply our results
• Sample= a group of people selected from the target population on who we conduct our research on
• A representative sample enables us to generalise our results to a target population- if it is unrepresentative of the population, it is said to be biased
• Opportunity sampling= selecting people who are most easily available

  • less costly & time-consuming
  • sample may be easily biased- more likely to approach some people & it automatically excludes some people depending on where you are.
• Volunteer sampling= psychologists advertise for pps and use those who volunteer

  • people who volunteer tend to be unrepresentative- as they have the extra time on their hands to do so
  • people who volunteer may have a certain personality type- eg they may be more compliant
  • this sampling is potentially high in representativeness if the request reaches a large number of people.
• Systematic sampling= use of a predetermined system to select pps using a numerical interval which is applied consistently, eg every 6th person in a phonebook

  • bias is reduced; researcher removed from the selection process
  • no guarantee that selected people will take part- may skew the sample
• Random sampling= all members of target population have an equal chance of getting chosen- use random selection methods to choose the amount of people you need

  • potentially unbiased- if you can identify every member of target population
  • bias may still occur as people may refuse to take part
  • every member of target population must be identified which may be difficult & time consuming
• Stratified sampling= important sub-groups within the target population are identified, sample then made up of the correct proportion of sub group

  • potentially highly representative of target population
  • can be very difficult & time-consuming
  • may still be bias within each subgroup
  • gets around the issue of having to give every member of the target population the equal chance of being selected.
• In sampling, start with general population, then develop a target population and then you must take a sample.