EXPERIMENTAL DESIGNS

• independent groups

  one group does condition a and the second does condition b. participants should be randomly allocated to experimental groups
• benefits of independent groups

  no order effects - only tested once so cant become bored/tired . controls confounding variables

  no demand characteristics - only tested once so unlikely to guess aim. Behaviour may be more natural
• weaknesses of independent groups

  participant variables - participants in the two groups are different so they act as EV/CV

  less economical - need twice as many Ps as repeated measures for the same data
• Repeated measures

  same participants take place in all conditions of an experiment

  the order of conditions should be counterbalanced to avoid order effects
• benefits of repeated measures

  participant variables - same people in each . Controls an important CV

  Fewer participants - less time and money spent recruiting
• weaknesses of repeated measures

  Order effects - participants may do better/worse after one task. reduces the validity

  Demand Characteristics - may change their behaviour if they find out the aim. reduces the validity
• matched pairs

  two groups of participants paired based on participant variables that matter for the experiment
• benefits of matched pairs

  Participant Variables - Ps are matched on a relevant variable. increased validity

  No order effects - only tested once. increased validity
• weaknesses of matched pairs

  Matching is not perfect and very time consuming. cant address all participant variables

  more participants are needed costing time and money