control, demand characteristics and investigator effects

• control

  • how researchers know how to control/eliminate extraneous variables through:
  • random allocation
  • counterbalancing
  • randomisation
  • standardisation
• what are extraneous variables?

  • any variable other than the IV that may affect the DV and results
• what are the types of extraneous variables?

  • situational variables- variables connected with the research situation e.g. temperature time of day. they are controlled through standardisation (ensuring temperature is the same for both groups)
  • participant variables- variables connected with the participants e.g. age, gender. they're controlled through the experimental design (matched pairs or random allocation to help reduce bias)
• random allocation

  • randomly allocating participants to their groups to decrease the possibility that participant variables I the form of individual differences such as IQ will affect the results
• counterbalancing

  • to combat the problem of order effects with repeated measures design , researchers can counterbalance the order of the conditions
  • sample is split in half with one half completing the 2 conditions in one order and the other half completing them in the reverse order
  • any order effects should be balanced out by the opposing half of participants
• randomisation

  • when trials are presented in a random order to avoid any bias the order of the trials may present
• standardisation

  • process in which all situational variables of a procedure used in research are kept identical
  • changes in data can be attributed to the IV under these conditions
  • standardisation means's far more likely the results will be replicated on different occasions
• demand characteristics and investigator effects
• demand characteristics and investigator effects

  • both act as confounding variables which affects the results of the research
  • demand characteristics occur when the participants try to make sense of the research and change their behaviour according to try and meet the aims of the research
• how are demand characteristics controlled?

  -not allowing participants to guess the aim or identify the IV

  -this is achieved by using a single-blind experimental technique (only the researcher knows the true aim). an example of this is when comparing the effects of a therapeutic drug with a placebo, only the researcher knows which is which
• what are investigator effects?

  • when a researcher consciously or unconsciously acts in a way to support their prediction.
  • this can be a problem when observing events which can be interpreted in more than one way
  • e.g. one researcher may view children fighting as violence whereas another may view it as rough play