Experimental Design

• Repeated measures


  all ppts experience both conditions in the experiment

  Advantages:

  - ppts variables are controlled

  - fewer ppts needed -> less time spent

  Disadvantages:

  - each ppts has to do at least 2 tasks -> order may be significant, can create boredom - order effect

  Remedy to disadvantages:

  - researchers use counterbalancing
• Independent measures


  when 2 separate groups experience 2 different conditions in an experiment

  Advantages:

  - order effects aren't a problem

  - ppts are less likely to guess aims

  Disadvantages:

  - ppts in different groups aren't the same in terms of ppt variables

  - DV may be affected more by ppt variables than IV

  Remedy to disadvantages:

  - use random allocation
• Matched pairs


  ppts are paired together on a variable(s) of the experiment

  Advantages:

  -single condition means order effect + demand characteristics are less of a problem

  Disadvantages:

  - ppts can't be matched exactly

  - matching can be time consuming + expensive

  - less economical
• Counterbalancing


  reducing order effects has half the ppts doing one condition first and other half of the ppts the same condition second.
• Randomisation


  rather than ppts alternating experiencing one condition first, then the other, researchers randomly assign whether ppts do one or other condition first