experimental design

• independent groups 


  An experimental design where each participants only takes part in one condition of the IV
• evaluation of independent groups 


  • Order effects cannot be observed, as no participants will be used in more than one condition.
  • Data collection will be less time-consuming if all conditions of the experiment can be conducted simultaneously.
  • Different participants need to be recruited for each condition, which can be difficult and expensive.
  • There is a risk of participant variables (individual differences between participants) affecting the results between conditions, rather than solely manipulation of the independent variable.
• repeated measures 


  An experimental design where each participants takes part in both/all conditions of the IV
• evaluation of repeated measures

  • The results will not subject to participant variables , putting confidence in DV changes being due to manipulated changes in the IV
  • same participants are used at least twice, extra participants don't need to be recruited.
  • risk of order effects,risk reduced by counterbalancing (controlling the order of variables so that each order combination occurs same number of times, e.g. one half of participants partake in condition A followed by B, other half partake in B followed by A).
  • If participant drops out, data lost from all conditions of the experiment
• matched pairs 


  An experimental design where pairs of participants are matched on important characteristics and one member allocated to each condition of the IV
• evaluation of matched pairs 


  • Order effects will not be observed as participants only take part in one condition.
  • The tailored participant-matching process reduces the risk of participant variables (individual differences) from affecting results between conditions.
  • Different participants need to be recruited for each condition, which is difficult and expensive.
  • Matching is a more complex process, and it will always be very difficult to match participants identically.