experimental design

• repeated measures


  • same people used in both conditions of the experiment and their performance in the two conditions compared
  • participant variables eliminated
  • order effects, include practise effects - ppts may perform better in the second condition as they had practice in the first and fatigue effects - ppts become bored or tired by the second condition
• independent measures


  • different participants perform in each condition and their performances are compared
  • no order effects
  • individual differences
• matched pairs 


  • different people perform in each condition but are matched in ways that are matched in ways that are important to the experiment (e.g IQ)
  • they are all pre tested for this variable and for each condition their matched pair is in the other one
  • individual differences reduced
  • difficult and time consuming to match pairs
• counterbalancing 


  • reduces the impact of order effects
  • ensures that each condition is tested first or second in equal amounts
  • e.g if scientists want to compare how people perform on tests A then B, they may perform better in test B because they have had practice so sceintists make 1 group do test B first and test A second