extraneous variables

investigator effects

  • body language
  • facial expressions
  • emphasising certain words
  • tone of voice

controlled by:

  • double blind design:

   - neither participant nor researcher knows the aim of the experiment

  • inter rater reliability

   - 2 researchers and you compare results

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Participant variables

  • mood
  • diet
  • sleep
  • IQ
  • fitness

controlled by:

  • Randomisation

- randomly allocating participants into groups

  • Dont use independent measures
  • counterbalance if using repeated measures

- ABBA technique balances out any order affects

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situational variables

  • time of day
  • noise
  • light

controlled by:

  • standardisation 

- keeping the procedure and instructions the same each time for every participant

  • counterbalance

- ABBA technique to balance out order effects

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demand characteristics

  • behaving the way you think you ought to
  • trying harder in a certain condition because you should do better in that condition
  • behaving formally in an interview

controlled by:

  • single blind design / deception

- the participant doesnt know the aim of the experiment

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