experimental design

• Experimental designs

  • Independent groups design
  • Repeated measures
  • Matched pairs
• independent group design


  different participants are used in each condition of the independent variable
• strengths of independent group design

  • avoids order effects as people participate in one condition only
• limitations in independent group design


  • no control over participant variables - different abilities of the participants in the various condiotions can cause changes to the DV
• improvement in independent group design

  • random allocation reduces the lack of control over participant variables as it ensures that each participant has the same chance of being in one condition of the IV as another
• repeated measures design


  the same participants participate in each independent variable condition
• strengths of repeated measures design

  • individual differences are resources
  • fewer people needed as they participate in all conditions - not as time consuming
• limitations of repeated measures design

  • order effects - performance can be worse due to fatigue (fatigue effect) or it may be better because they know what to do (practise effects)
• improvement in repeated measures design

  • counterbalancing - half of the participants do conditions in one order and the other half do it in the opposite order
• matched pairs


  pairs of participants are matched on some variable that has been found to affect the DV

  one member of each pair is then placed into the experimental group and the other into the control group
• strengths of matched pairs

  • no order effects
  • reduces participant variables as they are paired up with someone who shares similar characteristics
• limitations of matched pairs

  • time consuming to match up pairs
  • impossible to match people exactly, unless they're twins