Experimental designs

• Independent groups - each participant is in a separate group, so they are not exposed to each other's behaviour
• Advantages of independent groups design - No order effects
• Disadvantages of independent groups -

  Participant variables - differences between the people in each group may affect the results

  Number of participants - twice as many participants are needed to get the same amount of data, compared to having everyone do both designs (repeated measures)
• Repeated measures - the same participants are used in each condition of the experiment.
• Advantages of repeated measures -

  No participant variables (No differences between participants in different groups as there is only one group)

  Number of participants (Fewer participants are needed)
• Disadvantages of repeated measures-

  Order effects (when participants' responses in the various conditions are affected by the order of conditions to which they were exposed)
• Matched participant design - participants are matched on a variable of interest, such as gender, age, or personality
• Advantages of matched pairs -

  No order effects (different people in each condition)

  Fewer participant variables (minimised through matching)
• Disadvantages of matched pairs -

  Number of participants (need twice as many people compared to repeated measures)

  Time-consuming and costly (as it could be difficult to find participants that match)
• Counter balancing - Counterbalancing is a technique used to deal with order effects when using a repeated measures design. With counterbalancing, the participant sample is divided in half, with one half completing the two conditions in one order and the other half completing the conditions in the reverse order
• Random allocation - participants are randomly allocated to each condition, so that each participant has an equal chance of being in each condition (e.g. by drawing names out a hat)