Experimental Design

• Independent groups

  Two groups are exposed to different experimental conditions, so PPs only experience one condition of the IV, generating unrelated data

  
  

  Strengths:

  • no order effects (when a PPs response is affected by order of conditions exposed to)
  • demand characteristics are unlikely since PPs are only exposed to one condition so are less likely to guess the aim (internal validity)

  Weaknesses:

  • if more participants with a particular characteristic are all randomly allocated to one condition then this presents an unfair representation (decreases validity of findings)
• Repeated measures

  When the same PPs take part in all conditions of the independent variable, producing related data

  Strengths:

  • the PPs act as their own control group since their data is compared against their own performance, so participant variables aren't an issue

  Weaknesses:

  • PPs take part in multiple conditions so may guess the aim of the experiment (demand characteristics) which secreases internal validity
  • order effects may lower validity of study (PPs may become bored or overly practised at the study)
• Matched pairs

  PPs are matched based on specific characteristics or variable that are important for the research

  Strengths:

  • demand characteristics are reduced because PPs take part in the only condition of the IV

  Weaknesses:

  • very difficult to match pairs identically and they can't be matched on every level
  • requires more PPs