Experimental designs

• Experimental designs-

  • how participants are used in experiments and allocated for different conditions
• Independent groups-

  • different participants in each condition
  • only complete one condition of the independent variable
  • randomly allocated to try and balance differences, results compared
  • S- no order effects
  • S- less chance of guessing the purpose
  • S- fewer demand characteristics
  • S- no participants lost between conditions
  • W- people aren’t the same, could effect results
  • W- more participants needed- expensive, time consuming, less economical
• Repeated measure design-

  • all participants in both conditions (experimental and control)
  • the means from both are compared
  • S- no individual diffrences
  • S- fewer participants needed
  • W-lost participants if dropped out
  • W- time breaks needed between conditions
  • W- order effects, makes participants repeat the experiment
  • W- Order effects can be reduced by counter balancing (demand characteristics)
• Matched pairs design-

  • Similar participants used in each condition
  • matched on any characteristics that would be important with impacting the experiment
  • pilot studies are done for effective matching
  • S- participants differences are closely matched
  • S- no order effects
  • S- demand characteristics are limited
  • W- matching is difficult
  • W- time consuming for accuracy
  • W- more participants needed