sampling

• target population - who research is aimed at
• sample - those taking part in research
• to generalise to wider population, sample needs to be representative, if not then sample is biased
• random sampling - every member of target population has equal chance of being selected
• opportunity sampling - researcher selects participants that are available at the time
• volunteer sampling - sample consists of individuals who've determined their involvement
• systematic sampling - sample obtained by selecting every nth person from list

  -numerical interval applied constantly
• stratified sampling - dividing target population into important sub-categories

  -randomly selecting members of sub-categories in correct proportions
• advantages of random - provides good chance of representative sample
• disadvantages of random - compiling list of everyone in TP is impractical

  -chance lead to biased sample in small numbers
• advantages of opportunity - convenient

  -quick

  -economical
• disadvantages of opportunity - unrepresentative

  -often biased
• advantages of volunteer - saves lot of time

  -economical
• disadvantages of volunteer - unrepresentative as similar type of people volunteer
• advantages of systematic - unbiased (selected using objective system)
• disadvantages of systematic - not truly unbiased / random unless select a number using random method
• advantages of stratified - representative (proportional)
• disadvantages of stratified - very time consuming (to identify subgroups)
• event sampling - record how many times certain behaviour occurs in set amount of time
• time sampling - record what behaviours are occurring at different time intervals
• point sampling - record what behaviours just one P in group is doing