!!! sampling

• representative sample

  participants in the sample are similar to those in the population

  similar = gender, class, ethnic status, intelligence etc
• techniques - random sampling

  • all population has an equal chance of being selected
  • can be done by computer generating, names/numbers in a hat, pin technique (half for condition 1, half for condition 2)
• random sampling evaluation

  strengths:

  • no researcher bias

  weaknesses:

  • may not be representative
• techniques - opportunity sampling

  • selected based on who is willing and avaliable at the time of the study
• opportunity sampling evaluation

  strengths

  • practically efficient way of producing a sample of data quickly weaknesses
  • may not be representative, so cannot be generalised
  • not random as researcher chooses the sample, so there is bias
• techniques - systematic sampling

  • every nth member selected, population is divided by sample size
• systematic sampling evaluation

  strengths

  • reduces sampling bias - not chosen by researcher
  • not based on who is avaliable at the time of the study

  weaknesses

  • may not be representative - so cannot be generalised e.g., every nth person could be male
• techniques - volunteer sampling


  people respond to an advert and come forward to take part
• volunteer sampling evaluation

  strengths

  • gathering the sample takes little effort
  • less time consuming than other methods

  weaknesses

  • may not be representative - cannot generalise as a certain type of person may volunteer
• techniques - stratified sample

  • strata in the population is identified
  • work out proportions/ratios
  • sample is randomly selected to match population
• stratified sample evaluation

  strengths

  • based on ratios - produces a truly representative sample

  weaknesses

  • impractical
  • time consuming
• pilot studies

  • small scale practice investigations
  • carried out prior to main research
  • done to identify potential problems with design, methods or analysis so they can be rectified
  • participants may also suggest changes like making demand characteristics harder to react to or making instructions clearer
  • will improve reliability and validity of the final research