Experimental design

• Independent groups are when one group does condition A and a second group does condition B. Also, participants should be randomly allocated to each condition.

  
  

  +) Participants only tested once so are unlikely to guess the aims.

  -) The participants in the two conditions are different making them extraneous/confounding variables.
• Repeated measures are when the same participants take part in all conditions of an experiment.

  
  

  +) The person in both conditions has the same characteristics, controlling an important confounding variable.

  -) Participants may do better/worse when doing a similar task twice (Order of effects)

  -> Order of conditions should be counterbalanced to avoid order effects.
• Matched pairs is when there are two groups of participants but they are related to eachother by being paired on participant variables that are relevant to the experiment.

  
  

  +) Participants are only tested once so no order effects.

  -) Matching participants is time-consuming and you cant control all relevant variables.