Sampling

• What is the target population?

  Group of individuals researcher interested in.
• What is the sampling frame?

  Smaller group of people in target population from which sample is drawn from.
• What is opportunity sampling?


  Sample of participants produced by selecting people who are most easily available at time of study.
• Advantage of opportunity sampling?

  Easy as it takes less time
• Disadvantage of opportunity sampling?

  Biased as sample drawn from small part of target population.
• What is random sampling?


  Sample of participants produced by using random technique so every member of target population being tested has equal chance of being selected.
• Advantage of random sampling?


  Unbiased as all members of target population have equal chance of selection.
• What is snowball sampling?


  Relies on referrals from initial participants to generate additional participants.
• Advantage of snowball sampling?


  Enables researcher to locate groups of people difficult to access e.g, drug addicts.
• Disadvantage of snowball sampling?


  Sample not likely to be good cross-section from population as it's friends of friends.
• What is self-selected sampling?


  Relies solely on volunteers to make up sample.
• Advantages of self-selected sampling?


  Access to variety of participants- may make sample more representative & less biased.
• Disadvantage of self-selected sampling?

  Sample biased as participants likely to be more highly motivated to be helpful &/or with extra time on hands (volunteer bias).
• What is stratified sampling?


  Sample produced by identifying subgroups according to their frequency in target population. Participants then selected randomly from subgroups.
• Advantage of stratified sampling?


  More representative as there's a proportional representation of subgroups.
• Disadvantage of stratified sampling?


  Time-consuming to identify subgroups & then select people & contact them.
• What is systematic sampling?


  Selecting every nth person ( n is a number). Can be a random sample if first person is selected using a random method, & then select every nth person after that.
• Advantage of systematic sampling?


  Unbiased as participants selected using objective system.
• Disadvantages of systematic sampling?


  Not truly unbiased/random unless you select a number using random method & start with this person & then select every nth person.
• What is quota sampling?

  Similar to stratified except participants not selected from strata using random sampling technique.
• What is bias?


  A systematic distortion
• What is generalisation?


  Applying findings of particular study to target population