strengths + weaknesses of research/experimental designs

• weaknesses of repeated measures

  1. order effect could affect results
  2. as participants see the task more than once they have increased exposure to demand characteristics
• strengths of repeated measures

  • fewer participants. so is good when participants are hard to find
  • as each participant does all the IV levels, participant variables are unlikely to distort it
• strengths of matched pairs/participants

  • one level of the IV reduces the effect of demand characteristics
  • no order effects
  • individual differences are matched so participant variable = less likely to distort effect of IV
• weaknesses of matched pairs/participants

  • small sample size as availability of matching pairs is limited
  • similarity between pairs is limited by matching process so correct criteria must be chosen to prove effectiveness
• weaknesses of independent measures

  • more participants needed = less ethical if they are harmed + less effective if there is a small sample as they're hard to find
  • participant variables can distort results if there are important individual differences between participants in diff levels of IV
• strengths of independent measures

  • diff participants used in each IV level = reduces order effects
  • effect of demand characteristics reduces as ppts only see 1 IV lvl
  • random allocation of IV lvl = reduces effect of individual diffrences
• strengths of laboratory experiments

  • good control of extraneous variables
  • casual relationships = determined
  • standardised procedures raise reliability + allow replication
• weaknesses of laboratory experiments

  • artificial behaviour can make ptcpnts behaviour unrepresentative
  • ptcpnts cld respond to demand characteristics + alter behaviour
• strengths of field experiments

  • ptcpnts in normal situation + more likely to behave naturally = representative results
  • ptcpnts unaware they are in study = less problems w demand characteristics than lab experiments
• weaknesses of field experiments

  • controlling extraneous variables = harder in lab exp = low reliability + difficulty to replicate
  • researcher = less sure changes in DV are caused by changes in IV than in lab exp
  • ptcpnts = unaware they are in a study - raising ethical issues
• strengths of quasi experiments

  • useful when unethical to manipulate IV
  • studies "real effects" so there is increased realism and ecological validity
• weaknesses of quasi experiments

  • must wait for IV to occur
  • can only be used where conditions vary naturally
  • ptcpnts = aware they are studies = less internal validity
  • confounding environmental variables = more likely = less reliable