Sampling

• What are sampling techniques?

  Method used to select people from the population
• What is a population?

  A group of people who are the focus of researcher's interest
• What is a sample?

  A group of people who take part in a research investigation. The sample is drawn from a population
• What is a random sample?

  All the members of the target population have an equal chance of being selected - first get list of all members of population, then assign numbers to names, then pick numbers from a hat
• What are the sampling techniques

  Random

  Systematic

  Stratified

  Opportunity

  Volunteer
• What is a systematic sample?

  When every nth member of the target population is selected
• What is an opportunity sample

  Researcher asks whoever is around and available at the time of their study e.g. in the street
• What is a volunteer sample?

  Ppts select themselves to be part of the sample (find out through advertisment)
• Advantages of random sample

  • Unbiased - extraneous variables are equally divided between diff groups - enhance internal validity
• Disadvantages of random sample

  • Difficult and time-consuming to conduct as complete list of target population is hard to obtain
  • Selected ppts may refuse to take part meaning you end up with more of a volunteer sample
• Advantages of systematic

  • Objective and well controlled
• Disadvantages of systematic

  • Time-consuming
  • Ppts may refuse to take part
• Advantages of stratified sample

  • Representative as it is designed accurately to reflect composition of the population
• Disadvantages of stratified

  • Identified strata cannot reflect all ways that people are different so complete representation is not possible
• Advantages of opportunity

  • Convenient
  • Less expensive
• Disadvantages of opportunity

  • Unrepresentative of target population as sample is drawn from a specific area
  • Researcher bias - researcher has all control over who they choose for sample, may avoid people they don't like the look of
• Advantages of volunteer

  • Minimal effort from researcher
  • Easy to get volunteers with advertisement
  • Less time-consuming
  • Ppts are more engaged as they opted to be here
• Disadvantages of volunteer

  • Volunteer bias - volunteers may try to please the researcher so findings can't always be generalised