Sampling

• A target population is the group of people the psychologist wants to be able to generalise their findings to. A sample is the group of people selected to represent this group.
• Opportunity sampling is when you make use of the people who are readily available to you and willing to participate.

  + Quickest, easiest and most practical sampling method.

  _ Likely to produce sampling bias as certain types of people will be selected from limited areas reducing how representative it is.
• Volunteer sampling is when psychologists place an advert for participation in a study and interested people respond to the advert. The psychologist then selects the sample based on who fits their target population.

  + Wide range of potential participants.

  + Ethical as gives informed consent when the advert is detailed.

  _ Produces sampling bias as only a certain type of people tend to respond to adverts (e.g. more extroverted)
• Random sampling is when every member of the target population is equally likely to be selected who are then randomly selected.

  + Least biased sampling method as all members of the target population have an equal chance of being chosen.

  _ Difficult and time consuming especially with large target populations.
• Snowball sampling is achieved by asking a participant to ask someone else in the target population to participate.

  + Can be used in target populations where no list/cluster exists (e.g. drug users, criminals)

  _ No way of knowing how representative the sample is as the researchers have no control.