experimental designs

• what types of experimental designs are there

  repeated measure

  independent groups

  matched pairs
• what is a an experimental design


  its an overall plan for the participants in the study- the different ways in which participants can be organised into the experimental conditions

  basically its what we do with them in an experiment
• what is an independent groups design

  this is when two completely different groups of people are used. they are independent from each other- people in each group will know nothing about the other condition
• what is a repeated measures design

  only one group of participants is used. all participants do both conditions. they repeat the study
• what is a matched pairs design

  this is when two groups are participants are used, each participant from one condition will be matched with another participant from the other condition. these pairings are based on relevant variables e.g. age, sex, IQ to the experiment. this makes both conditions as similar as possible
• advantages and disadvantages of independent groups design?

  • advantages- participants only know about one condition in experiment so they are less likely to catch on to what its about, they will not suffer from the boredom of having to do both conditions and will not be able to practice- these problems are called order effects
  • disadvantages- individual differences between people called participant variables can be a problem, also the experimenter will need to find twice as many participants when using this design
• what's an order effect

  these are issues that arise from the order that the conditions are presented in
• advantages and disadvantages of a repeated measures design?

  • advantages- lack of participant variables because we are comparing the same persons performance in one condition with their performance in the other making it a fair test.
  • disadvantages- order effects are a problem e.g. may begin to understand aim of experiment so may change their behavior, they will be able to practice, conditions might not be done on same day so things like mood or weather could change
• advantages and disadvantages of a matched participants design?

  • advantages- solves both problems of order effects and participant variables but it is not used often because of practical difficulties
  • disadvantages- difficult and time consuming to match participants, may not always be obvious which variables are important to match them on or they may be difficult to measure, also if one participant drops out the study we have to exclude their pair as well
• What does random allocation mean

  When you randomly allocate participants (we use this to control for participant variables)
• What is counterbalancing?


  • This is a useful way to minimise order effects in a repeated measures design
  • Two groups
  • Group 1 does condition A then condition B
  • Group 2 does condition B then condition A
• What is a naive participant

  Someone who is not aware of the experiment hypothesis (not a confederate). sometimes they don’t know they are in a study