sampling

• oppourtunity

  • anyone who is available (e.g asking around school)
  • quick and easy to obtain participants
  • not always representative and difficult to generalise
• random 


  • everyone in the target population has an equal chance (e.g drawing names out of a hat)
  • more likely to be representative of the target population
  • time consuming
• stratified 


  • identify subgroups and then choose a proportionate sample from them (e.g randomly taking a sample from different groups of students in college)
  • all subgroups are representative
  • can be difficult to identify subgroups
• systematic 


  • use a predetermined system (every nth person)
  • unbiased and objective
  • only truly unbiased if you select a number using a random method
• volunteer


  • people offer to be in the study
  • saves time
  • biased as ppts are likely to be highly motivated and have a lot of time on their hands
• random allocation

  • lottery method - obtain a list of all people in target population, put all names in a hat, first 10 go to condition 1 and second 10 go to condition 2
  • random number generator using computers and phones - number every member of the population and generate random numbers for the group