Experimental designs

• An independent group design is when a group of participants experience two different conditions of the experiment. Pps are randomly allocated to each condition to ensure a range of people in each group
• RE PE ATED MEA SU RES D ES IGN This is when all participants

  experience both conditions of the

  experiment. When repeated measures is used

  counterbalancing is sometimes

  used to balance out any order

  effects

  Order effects refer to the order

  of the conditions

  having an effect

  on the

  participants'

  behavior.

  Performance in

  the second

  condition may be

  better because

  the participants

  know what to do

  (i.e. practice

  effect).
• In a matched pairs deign, participants will be ‘matched’ to a participant in the other group on an important variable/key characteristic.
• What is one advantage of using independent groups in research?


  No order effects
• Why do independent groups reduce the risk of demand characteristics?


  Participants are less likely to guess the aim as they take part in one condition.
• What is a disadvantage of using independent groups in research?


  You need more participants as each can only be used once.
• How can participant variables affect the results in independent groups?


  Individual differences between participants may affect the results rather than solely the manipulation of the independent variable.
• Why is using independent groups considered less economical?


  It requires twice as many participants to produce equivalent data.
• REPEATED MEASURES Advantages • The results will not be subject to participant variables as the same group is used in each condition, fewer participants are needed therefore less time spent recruiting. Disadvantages • It is likely participants will work out the aim of the study when they experience all conditions of the experiment. Demand characteristics • Order effects may be present (participants becoming tired, bored or practiced from the first condition) – use counterbalancing to balance this
• What are the implications of needing more participants in independent groups?


  It increases the time and money spent on recruiting participants.
• Counterbalancing is a technique used to deal with order effects when using a repeated measures design

  Half of the participants experience the condition in one order and the other half in the opposite order
• Counterbalancing does not eliminate order effect but it distributes them evenly across all experimental conditions so that their influence is “balanced
• MATCHED PAIRS • Advantages • No order effects as pps only take part in one condition • Minimise demand characteristics • The tailored participant-matching process reduces the risk of participant variables (individual differences) from affecting results between conditions.

  Disadvantages Matching is a more complex process and often not enough pps to matches identically. Requires more ppts Time consuming and expensive
• Experimental design refers to how participants are allocated to each condition of the independent variable, such as a control or experimental group