Sampling and Pilot studies

• Sampling


  A selection of the target population that a researcher is interested in studying
• Target population


  The particular group of people a researcher is interested in studying
• Representative sample


  The sample population must be representative of the target population, so that the findings can be generalised from the sample back to the target population
• Biased sample


  If the sample is not representative of the target population, the sample is said to be biased
• Types of sampling


  • Opportunity sampling
  • Volunteer sampling
  • Random sampling
  • Systematic sampling
  • Stratified sampling
• Opportunity sampling


  • Easiest method to use
  • Biased because the sample is drawn from a small part of the target population, this means it won't be representative
• Volunteer sampling


  • No ethical issues as participants have chosen to take part
  • Gives you access to a variety of participants
  • Volunteer bias because participants are usually more highly motivated or have time on their hands, therefore it won't be representative
• Random sampling


  • Least biased- all members of the target population have an equal chance of being selected so are more likely to be representative
  • No guarantee that the sample will be representative
• Systematic sampling


  • Avoids research bias- once the system is selected, the researcher has no influence over who is chosen
  • No guarantee that the sample will be representative
• Stratified sampling


  • Representative sample as it will reflect all sub groups within the population- high population validity
  • The identified strata cannot reflect all the ways participants are different so is not fully representative
• Pilot study


  A small scale trial of a research design run before doing the real thing. Its aim is to check procedures and materials e.g instructions understood, fatigue/boredom due to too many questions
• Pilot studies can save time and money in the long run & increase the validity of the research