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Physical Variables Social Variables Personality Variables Context Variables PowerPoint Presentation
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Physical Variables Social Variables Personality Variables Context Variables
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  1. Physical Variables Social Variables Personality Variables Context Variables

  2. Physical variables are aspects of the testing situation that need to be controlled: • day of the week • experimental room • lighting What are physical variables? Physical Variables

  3. Elimination completely removes extraneous physical variables from the experimental situation (e.g., soundproofing a room). Removal of extraneous physical variables prevents them from operating differently across different treatment conditions. Explain elimination. Physical Variables

  4. Constancy of conditions controls extraneous physical variables by keeping all aspects of the treatment conditions identical, except for the independent variable.For example, test all subjects in the same room or at the same time of day. How does constancy of conditions work? Physical Variables

  5. Balancing controls extraneous physical variables by equally distributing their effects across treatment conditions. For example, running half of the subjects in each condition in the morning and half in the evening. How does balancing work? Physical Variables

  6. 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. In which order should you use these techniques? Physical Variables

  7. Social variables are aspects of the relationships between subjects and experimenters that can influence experimental results. These include demand characteristics and experimenter bias. What are social variables? Social Variables

  8. Demand characteristics are cues within the experimental situation that demand or elicit specific participant responses. Example: students cue professors to wrap up their lectures by packing their binders, books, and water bottles, and by looking at the door. Explain demand characteristics. Social Variables

  9. Demand characteristics can confound an experiment if they vary across experimental conditions. Subjects may act to confirm what they think is the experimental hypothesis. How can demand characteristics threaten internal validity? Social Variables

  10. In a single-blind experiment, subjects are not told their treatment condition. For example, in a single-blind drug study, the experimental and control groups might receive capsules that look and taste identical. What is a single-blind experiment? Social Variables

  11. When subjects are not told their treatment condition, this eliminates cues that might alter their behavior. How do single-blind experiments control demand characteristics? Social Variables

  12. The placebo effect is when a subject receives an inert treatment and improves because of positive expectancies. What is the placebo effect? Social Variables

  13. A cover story is a false plausible explanation of the experimental procedures to disguise the research hypothesis from the subjects. They should be used sparingly, since they are a form of deception. How do cover stories control demand characteristics? Social Variables

  14. Experimenter bias is any behavior by the experimenter that can confound the experiment. For example, an experimenter might provide more attention to subjects in one condition than another. What is experimenter bias? Social Variables

  15. The Rosenthal effect is the phenomenon in which experimenters treat subjects differently based on their expectations and their resulting actions influence subject performance. This is also called the Pygmalion effect and self-fulfilling prophecy. What is the Rosenthal effect? Social Variables

  16. For example, teachers might give more attention and feedback to high aptitude students than to low aptitude students. The Rosenthal effect can confound an experiment, producing results consistent with the experimenter’s expectations. What is the Rosenthal effect? Social Variables

  17. Single-blind experimentsonly control demand characteristics, since subjects are blinded to their condition. Double-blind experimentscontrol both demand characteristics and experimenter bias, since both the experimenter and subjects are blinded. Why is a double-blind design superior to a single-blind design in controlling experimenter bias? Social Variables

  18. Research on experimenter personality shows that when experimenters are warm and friendly, subjects learn more, talk more, earn better test scores, and are eager to please. Hostile or authoritarian experimenters obtain inferior subject performance. How might an experimenter's personality affect experimental results? Personality Variables

  19. Employ multiple experimenters to run an equal number of subjects in each of the experimental conditions (balancing).Treat “experimenter” as an independent variable in statistical analysis. If an interaction is found, then the experiment was confounded. How can experimenters control personality variables? Personality Variables

  20. When there is a single experimenter, minimize face-to-face contact and closely follow the script. Videotape sessions to confirm consistent performance. How can experimenters control personality variables? Personality Variables

  21. Volunteers are 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. How do volunteers differ from nonvolunteers? Personality Variables

  22. Context variables are extraneous variables produced by experimental procedures created by the research setting environment, like assignment of participants to conditions. What are context variables? Context Variables

  23. When we allow subjects to sign up for experiments whose titles differ in their appeal:“The Memory Test Experiment” “The Heavy Metal Music Experiment” However, this could result in a biased sample threatening external validity. When might subjects select the experiment? Context Variables

  24. Selecting your friends might bias your sample, threatening external validity. Both you and your friends might act differently in your experiment than strangers. Why shouldn’t you run your friends in your experiment? Context Variables

  25. Subjects who sign up late in the semester may be less motivated and may behave differently than those who sign up earlier in the semester. Rosenthal speculated that the differences seen at the start and end of an experiment may be just as likely due to changes in the experimenter. Summarize the folklore about subjects. Context Variables