Experimental designs

• What are the three types of experimental designs?

  Independent groups, repeated measures, matched pairs
• What is an independent groups design?

  Where two separate groups of participants experience two different conditions
• What is a repeated measures design?


  Where all participants experience both conditions of the experiment
• What is a matched pairs design?

  Where participants are paired on a variable or variables relevant to the experiment
• How would you do a matched pairs design?

  Participants matched > one participant from one pair would be allocated to a different condition of the experiment
• What is matched pairs an attempt to control for?

  Participant variables
• Strengths: Independent groups

  Order effects not a problem

  Less likely to guess aims
• Limitations: Independent groups

  Participants not the same in terms of participant variables - reduced validity

  Less economical
• Strengths: Repeated measures

  Participant variables controlled

  Few participants needed
• Limitations: Repeated measures


  Order effects

  Demand characteristics
• Strengths: Matched pairs

  Less demand characteristics/order effects
• Limitations: Matched pairs

  Still some participant variables

  Time-consuming and expensive
• How would a researcher deal with participant variables in an independent groups design?

  Random allocation
• What is random allocation?

  Evenly distributing participants randomly across all conditions
• How would you complete random allocation?

  Names in a hat or a name generator
• How would a researcher deal with order effects in a repeated measures design?

  Counterbalancing
• What is counterbalancing?

  Half the participants take part in condition A then B and the other half take part in condition B then A
• What band can be used to remember the order of counterbalancing?

  ABBA
• Counterbalancing attempts to balance out the effects of order effects
• Random allocation attempts to balance out the effects of participant variables