Methods of control

• Random allocation


  PP in independent groups design should be randomly allocated to one of the two experimental conditions.

  Ensures characteristics of PP don't differ greatly between conditions.

  allows researcher to maintain objectivity and reduce unconscious investigator effects.
• Counterbalancing 


  Involves equal numbers of PP undertaking the required condition of the IV in different orders. It's used as a way to balance out order effects which reduces validity.

  The original sample is split randomly into two groups: one group does condition A then B and other group does B then A.

  Results from B and B are combined and A and A are combined.

  This reduces order effects.
• Randomisation 


  Means having equal chance and when the material is presented to the participants in a random order.

  -order of words should be random

  -put them in a hat and pull numbers out randomly.

  -reduces influence of unconscious researcher effects
• Standardisation 


  ensures the experimenters act in a similar way with all PP (no researcher bias). Means everything should be as similar as possible for all PP e.g. same instructions, same environment, same questions. The only thing different between PP's is the IV.