CH 8

• Physical Variables


  Aspects of the testing situation that need to be controlled
• Physical Variables


  • day of the week
  • experimental room
  • lighting
• Elimination


  Completely removes extraneous physical variables from the experimental situation
• Constancy of conditions


  Controls extraneous physical variables by keeping all aspects of the treatment conditions identical, except for the independent variable
• Balancing


  Controls extraneous physical variables by equally distributing their effects across treatment conditions
• Techniques for controlling physical variables

  1. Eliminate extraneous variables whenever possible

  2. Keep conditions constant where elimination is not possible

  3. Balance the effects of extraneous variables when constancy of conditions is not possible
• Social Variables


  Aspects of the relationships between subjects and experimenters that can influence experimental results
• Demand characteristics


  Cues within the experimental situation that demand or elicit specific participant responses
• Demand characteristics


  Can confound an experiment if they vary across experimental conditions
• Single-blind experiment


  Subjects are not told their treatment condition
• Placebo effect


  When a subject receives an inert treatment and improves because of positive expectancies
• Cover story


  A false plausible explanation of the experimental procedures to disguise the research hypothesis from the subjects
• Experimenter bias


  Any behavior by the experimenter that can confound the experiment
• Rosenthal effect


  The phenomenon in which experimenters treat subjects differently based on their expectations and their resulting actions influence subject performance
• Double-blind design


  Superior to a single-blind design in controlling experimenter bias
• Personality Variables


  Aspects of the experimenter's personality that can affect experimental results
• Warm and friendly experimenters obtain better subject performance than hostile or authoritarian experimenters
• Controlling personality variables


  1. Employ multiple experimenters to run an equal number of subjects in each condition

  2. Treat "experimenter" as an independent variable in statistical analysis

  3. Minimize face-to-face contact and closely follow a script when there is a single experimenter
• Volunteers


  More sociable, score higher in social desirability, hold more liberal social and political attitudes, are less authoritarian, and score higher on intelligence tests than nonvolunteers
• Context Variables


  Extraneous variables produced by experimental procedures created by the research setting environment
• Allowing subjects to select the experiment

  Can result in a biased sample threatening external validity
• Selecting your friends as subjects

  Might bias your sample and threaten external validity
• Subjects who sign up late in the semester may be less motivated and may behave differently than those who sign up earlier
• Physical Variables


  Aspects of the testing situation that need to be controlled
• Physical Variables


  • day of the week
  • experimental room
  • lighting
• Elimination


  Completely removes extraneous physical variables from the experimental situation
• Constancy of conditions


  Controls extraneous physical variables by keeping all aspects of the treatment conditions identical, except for the independent variable
• Balancing


  Controls extraneous physical variables by equally distributing their effects across treatment conditions
• Order of techniques for physical variables

  1. Eliminate extraneous variables whenever possible

  2. Keep conditions constant where elimination is not possible

  3. Balance the effects of extraneous variables when constancy of conditions is not possible
• Social Variables


  Aspects of the relationships between subjects and experimenters that can influence experimental results
• Demand characteristics


  Cues within the experimental situation that demand or elicit specific participant responses
• Demand characteristics can confound an experiment if they vary across experimental conditions</b>
• Single-blind experiment


  Subjects are not told their treatment condition
• Placebo effect


  When a subject receives an inert treatment and improves because of positive expectancies
• Cover story


  A false plausible explanation of the experimental procedures to disguise the research hypothesis from the subjects
• Experimenter bias


  Any behavior by the experimenter that can confound the experiment
• Rosenthal effect


  The phenomenon in which experimenters treat subjects differently based on their expectations and their resulting actions influence subject performance
• Double-blind experiments control both demand characteristics and experimenter bias, since both the experimenter and subjects are blinded
• Personality Variables


  Aspects of the experimenter's personality that can influence experimental results
• Warm and friendly experimenters obtain better subject performance than hostile or authoritarian experimenters