Repeated measures

• • all participants experience all levels of the IV
  • compare DV of partic in each experiment
  • memory performance (DV) of partic is measured in 2 parts
• E.G.

  each partic does memory task after drinking caffeine, 1 week later, similar memory test is given to same partic without the caffeine
• Advantages


  • controls for partic variables: partic variables kept constant between conditions as the same partic takes part in all conditions
  • fewer partic needed = high ecological validity
• Disadvantages

  • order effects: partic given test on 2 diff occasions = higher performance in second test due to practice
  • demand characteristics: as partic takes part in all conditions, they may guess the aim of the study, and change behaviour accordingly
• Ways to deal with disadvantages

  • counterbalancing - A then B, B then A
  • deception - partic unaware of research aim, may raise ethical issues
• Counterbalancing


  • AB or BA - divide partic in 2 groups
  • - group 1 do A then B, group 2 do B then A
  • ABBA - all partic take part in each condition twice
  • - trial 1, condition A
  • trial 2, condition B
  • trial 3, condition B
  • trial 4, condition A