L8 CONTROLLING EXTRANEOUS

• physical variables - day of the week, testing room, noise and distractions
• physical variables - aspects of the testing conditions that can be controlled
• elimination - make sure that an extraneous variable does not affects an experiment, removal of extraneous variable
• constancy of conditions - we keep all aspects of the treatment conditions as nearly similar as possible, try to make sure that it stays the same in all treatment conditions
• physical variables that can be kept constant with a little effort:

  • time of testing
  • testing location
  • mechanical procedures
• balancing - distributing the effects of an extraneous variable across the different treatment conditions of the experiment
• ways in controlling physical variables

  • elimination
  • constancy
  • balancing
• balancing - if we cannot test all subjects at the same time of the day, we arrange things so that we test equal numbers of treatment
• things are fine - as long as there is no systematic change in an extraneous variable
• precautions to set up a reasonably good experiment:

  • eliminate extraneous variables
  • keep treatment conditions as similar as possible
  • balance out the effects of other variables
  • assign individual subjects to treatment conditions at random
• internal validity - do not sacrifice this for external validity
• social variables - qualities of relationships between subjects and experimenters that can influence results
• demand characteristics - demand that people behave in a particular way
• demand characteristics - they want to conform to what they think is the proper role of a subjects
• single-blind experiment - subjects do not know which treatment they are getting
• single-blind experiment - we can disclose some but not all information about the experiment to subjects, disclose what is going to happen to them in the experiment, keep them fully informed about the purpose of the study
• placebo effect - researchers know that if you give a person any pill, the person is apt to say that the pill helped
• placebo - pill, injection or other treatment that contains none of the actual medications
• cover story - plausible but false explanation for the procedures used in the study
• cover story - disguise the actual research hypothesis so that subjects will not guess what it is
• controlling demand characteristics:

  • single-blind experiment
  • cover story
• experimenter bias - the experimenter does something that creates confounding in the experiment
• rosenthal effect - experimenters might also treat subjects differently depending on what they expect from them, they might give more time to subjects who have gone through a particular treatment
• pygmalion effect - other term for rosenthal effect
• rosenthal effect - can be another source of confounding in an experiment
• double-blind experiment - subjects do not know which treatment they are receiving and the experimenter does not know either
• double-blind experiment - if the experimenter does not know which treatment the subject is getting, he or she cannot bias the responses in any systematic way
• personality variables - personal characteristics that an experimenter brings to the experimental setting
• context variables - come about from procedures created by the environment or context of the research setting
• context variables include:

  • subject recruitment
  • selection and assignment of procedures
  • typical problems encountered in research
• 2 basic kinds of context variables:

  • when subjects select their own experiment
  • when experimenters select their own subjects