Sampling

• What is the target population?


  the particular group of people the psychologists want to be able to generalise their findings to (need a varied sample to avoid bias, want to be able to generalise findings to improve society)
• What is a sample


  the group of people selected to represent the target population; these are the people studied in research - their behaviour is measured
• What is sampling

  the process of selecting participants from the population
• What is the problem with sampling bias


  it means we're unable to generalise results to the target population
• What are some examples of problems with generalisability


  only studying people from one area, age bias, gender bias or may only be reflective of one type of ethnic origin
• What are the four different types of sampling methods

  • opportunity sampling
  • volunteer/self selecting sample
  • random sampling
  • snowball sampling
• What is opportunity sampling


  making use of people that are "readily available to you (need to say in exam)" and willing to participate
• What is volunteer/self selecting sample


  people who want to take part in research volunteer themselves. psychologists put out an "advert (must say)", people reply to advert and psychologist filter responses and collect a sample that reflect target population
• What is random sampling

  "every member of the target population has an equal chance of being selected (must say in exam)", all potential participants entered into a draw + randomly selected
• What is snowball sampling 


  used if target population is hard to reach e.g drug users, criminals. ask participants to suggest someone else who might be willing or appropriate for study
• What does representative mean


  reflect the target population
• Strengths of opportunity sampling


  Point = is the easiest, quickest and most economical way to obtain participants as the psychologists will use people they have easy access to and they don't have to pay for advertising

  Comment = useful for gathering a representative sample and spending more time exploring the behaviour and analysing results
• Weakness of opportunity sampling

  P= likely to produce a bias as only certain types of people will be selected from limited areas; therefore it isn't very representative

  the researcher may also select people who look more friendly or willing to participate

  C= reduces generalisability of the behaviour to the target population
• Strengths of volunteer/self-selecting sample


  P= gives a wide range of access to potential participants. it is also convenient and ethical if it leads to informed consent and people will be less likely to drop out

  C= more representative of the target population as a wider group of people will see the advert
• Weakness of volunteer sampling 


  P= often unrepresentative as it leads to a bias sample, people tend not to respond to adverts etc unless they have a strong interest/view to share or a motivation to take part

  C= lowers the generalisability of the behaviour and can increase volunteer bias
• Strengths of random sampling 


  P= the least bias method of sampling as all members of the target population have an equal chance of being selected (and the researcher doesn't collect them)

  C= making it the most representative sampling method, meaning we can generalise the behaviour to the target population
• Weaknesses of random sampling 


  P= very difficult and time consuming to do, especially with large target populations

  C= limits the potential size so will lead to the sample's behaviour being less generalisable to the target population
• Strengths of snowball sampling 


  P= possible to include members of the group where no lists or identifiable clusters even exist (e.g drug abusers, criminals)

  C= we have representation groups that would otherwise not be researched
• Weakness of snowball sampling 


  P= there is no way of knowing whether the sample is representative of the population

  C= we don't truly know whether we can generalise the behaviour to the target population