sampling

• population

  group of people who are the focus of the researcher's interest

  a smaller sample is drawn from them
• sample

  group of people who take part in a research investigation

  drawn from the population and is presumed to be representative.
• bias

  when certain groups are over or under represented within the sample.

  limits the generalisations that can be made
• generalisation

  extent to which findings and conclusions from an investigation can be broadly applied to the population
• random sample

  when all members of the target population have an equal chance of being selected.
• strength of random sampling

  • potentially unbiased
• limitations of random sampling

  • difficult and time-consuming
  • sample may still be unrepresentative
  • selected participants may refuse to take part
• systematic sample

  every nth member of the target population is selected.
• strength of systematic sampling

  • objective method - researcher has no influence over who is chosen
• limitation of systematic sampling

  • time-consuming
  • participants may refuse to take part
• stratified sample

  • composition of the sample reflects the proportions of people in certain subgroups (strata) within the target population
• strength of stratified sampling

  • produces a representative sample so generalisation is possible
• limitation of stratified sampling

  • cannot reflect all the ways people are different so it isn't completely representative
• opportunity sample

  made up of people who happen to be willing and available
• strength of opportunity sampling

  • convenient and less costly
• limitations of opportunity sampling

  • suffers from researcher bias
  • sampling is unrepresentative as it is taken from a specific area
• volunteer sampling

  participants select themselves to be part of the sample
• strengths of volunteer sampling

  • easy and less time consuming
  • participants will be more engaged as they chose to be there
• limitation of volunteer sampling

  • volunteer bias as people who choose to be in it may have a certain personality which affects how findings can be generalised.