Experimental designs

• Repeated Measures Design


  The same participants are allocated to all groups (i.e. take part in all conditions) of an experiment.

  Strengths; Results will not be subject to participant variables, putting more confidence in dependent variable changes

  Weaknesses; There is risk of observing order effects (e.g. practice / fatigue effects, or demand characteristics)
• Independent Groups Design

  Where different participants take part in each experimental condition

  Strengths

  • Order effects cannot be observed, as no participants will be used in more than one condition

  Weaknesses

  • 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
• Matched Pairs Design

  Participants take part in one experimental condition, but are recruited specifically to be similar in characteristics (e.g. intelligence, gender, age) to ‘matched’ participants in the other condition

  Strengths

  • Order effects will not be observed as participants only take part in one condition.
  • Participant-matching reduces the risk of participant variables from affecting results between conditions.

  Weaknesses

  • Different participants need to be recruited for each condition, which is difficult and expensive
  • Complex process, difficult to match participants identically.