Experimental Designs

• Repeated measures / related design


  Same paricipants take part in both conditions of the experiment
• Strengths of repeated measures


  - Eliminates individual differences as it compares performance of the same individual

  - Practical convenience as there is no need t recruit as many participants
• Weaknesses of repeated measures


  - Demand characteristics as participants may anticipate what the experiment is measuring and change their behaviour

  - Performance could improve (practice effects) or performance could deteriorate (fatigue effects)
• Independent measures / Unrelated designs


  Different participants take part in the different conditions of the experiment.
• Strengths of Independent measures / Unrelated designs


  - Eliminates order, practice and fatigue effects as participants only participate in one condition

  - Reduces demand characteristics as this reduces time that participants have to anticipate or produce socially desirable responses
• Weaknesses of Independent measures / Unrelated designs


  - Cost and convenience inefficient as twice as many participants required

  - Individual differences being responsible for the differences in results found in the two conditions
• Matched pairs design


  Participants are matched according to pre-defined criteria - one of pair allocated to condition A and the other to condition B
• Strengths of matched pairs design


  - Reduce the chance of participant variables, no practice or order effects

  - Reduces demand characteristics
• Weaknesses of matched pairs design


  - Time consuming to match participants