variables and controls

• What is an extraneous variable?

  A random variable affecting the results
• Why is it important to control extraneous variables?

  To prevent them from affecting results
• What is a confounding variable?

  A variable that varies with the IV
• What is the purpose of counterbalancing?

  To equally distribute order effects across conditions
• Outline the procedures of counterbalancing.

  • Participants are divided into two groups
  • One group completes conditions A then B
  • The other group completes conditions B then A
• What is the purpose of random allocation?

  To remove researcher bias in group allocation
• Outline the procedures of random allocation.

  • Write participants' names on paper
  • Place papers in a hat and shuffle
  • Blindly pull names for group allocation
• What is the purpose of randomisation?

  To randomly present stimuli in an unpredictable order
• Outline the procedures of randomisation.

  • Print stimuli on pieces of paper
  • Place papers in a hat and shuffle
  • Blindly pull papers for stimulus presentation
• What is the purpose of standardisation?

  To ensure all participants have the same experience
• Identify three ways to standardise a study.

  • Use the same instructions
  • Keep the location consistent
  • Ask the same questions
• Order effects

  When participants complete multiple conditions and so their performance could be affected by them having the chance to practice or become bored or fatigued.
• participant variables

  When participants’ performances could be affected by their individual differences such as their age, gender, IQ etc.
• investigator effects

  When participants’ performances could be affected by the characteristics and/or behaviours of the investigators e.g. their gender, age, the quality of the instructions they provide etc.
• Situational variables

  When participants’ performances could be affected by differences in the situation e.g. noise, lighting, temperature etc.
• task variables

  When participants’ performances could be affected by differences in the nature/difficulty of the tasks they are completing.
• procedure of counterbalancing

  Participants are grouped, with each group completing the conditions in a different order. To achieve this, participants are divided into two groups. One group complete condition A then B. Meanwhile the other group completes the

  conditions in the opposite order i.e. condition B then A.
• purpose of counterbalancing

  Used in a repeated measures design to equally distribute the impact of order effects (such as practice, boredom and

  fatigue) across conditions.
• the procedures of randomisation

  The researcher ensures a random order of stimuli by writing each one on separate pieces of paper, shuffling them in a hat, and blindly selecting them one by one until all have been assigned a position.
• discuss the purpose of randomisation

  Helps to reduce any predictable order. It therefore reduces the possibility that one condition will be easier than another (due to its predictability) and, in doing so, reduces the risk of task variablesfrom impacting the results.
• the procedures of standardization

  Involves keeping everything the same. This can include: using the same tasks or at least ensuring they are of the same difficulty; using the same researcher; providing the same instructions; and keeping the environment the same

  (noise/setting etc.)
• discuss the purpose of standardisation

  Ensures all participants have the same experience. This therefore helps to control task variables (by keeping the tasks the same/of equal difficulty), investigator effects (by keeping the researcher and their instructions the same), and situational variables(by keeping the environment the same).