experimental design

• Experimental designs are different ways in which participants can be organised in relation to the experimental conditions

  3 types of experimental design:

  • Independent groups
  • Repeated measures
  • Matched participants
• Independent groups design is where different participants are used in each condition of the IV.

  The performance of the 2 groups would then be compared.
• independent groups

  pros

  • Avoids order effects as pps are only in one condition,
  • Pps are less likely to guess the aim and show demand characteristics.

  cons

  • More people are needed so it is more time consuming
  • Individual difference between pps in the groups may affect the results (participant variables)
• Repeated measures is where all participants take part in all of the conditions of the experiment

  The results from each condition would then be compared to see if there was a difference
• repeated measures

  pros

  • As the same pps are used in each condition, participant variables are reduced
  • Fewer people are needed as they participate in all conditions

  cons

  • There may be order effects (where the order of conditions affects the pps behaviour) e.g. may perform better in the 2nd condition due to practice or may be tired in the 2nd condition
• Matched pairs is where pairs of participants are first matched on an extraneous variable, e.g. age, and then one is assigned to condition 1 and one is assigned to condition 2.
• matched pairs

  pros

  • Reduces participant variables as they have been paired on a characteristic
  • Avoids order effects as each pp is only in one condition

  cons

  • Very time consuming to try and find closely matched pairs and if you lose 1 pp, you lose 2
  • Pps can never be matched exactly