Control in experiments

• Define random allocation

  Putting ppts into conditions randomly. E.g. rather than first 20 people to arrive, go into 1 condition at random.
• Define counterbalancing

  The ppts are split into 2 groups / varies the order of conditions

  In group 1 they go through condition A then B.

  In group 2 (opposite) they go through condition B then A
• Define randomisation

  Tasks & stimulus must be presented in a random order to gain an accurate representation of behaviour.
• Define standardisation

  When all control variables are kept the same. Every participant has the same experience. Often relies on a script or printed set of instructions.
• Define demand characteristics

  Ppts try to make sense of the research and change their natural behaviour accordingly to support what they believe are the aims of the investigation. = Makes the results lack validity.

  In addition, the ppts may deliberately disrupt the results = a phenomenon known as the 'screw - you' effect.
• How can demand characteristics be controlled?Give an example

  By not allowing the ppt to guess the aim of the research / the identity of the IV through using a single-blind experimental technique = only the researcher knows the true aim (deception use).

  Therefore, the ppts are unable to try and either support or undermine the research on purpose.

  Example: Medical tests when comparing the effects of a therapeutic drug with a placebo, only the r knows which is which.
• Define investigator effects and a problem

  Where a researcher (consciously or unconsciously) acts in a way to support their prediction. This can be a problem when observing events that can be interpreted in more than one way.
• How can investigator effects be controlled? Give an example

  By not allowing either the ppts or the researcher to know the aim of the research and/or the identity of the IV through using a double-blind experiment technique = only the person who originally designed the experiment knows the true aim. (deception use)

  Therefore, consciously or unconsciously, the researcher is unable to influence the ppts

  Example: Medical test comparing the effectiveness of a therapeutic drug with a placebo, both r and ppt dont know which is which.