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Chapter 7

Chapter 7. Experience Carefully Planned : Experimental Research Designs. Advantage of Laboratory Experiments. Laboratory experiments allow researchers to see how things turn out when one and only one thing is changed. Two Necessities of True Experiments. Manipulation

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Chapter 7

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  1. Chapter 7 Experience Carefully Planned: Experimental Research Designs

  2. Advantage of Laboratory Experiments • Laboratory experiments allow researchers to see how things turn out when one and only one thing is changed

  3. Two Necessities of True Experiments • Manipulation • Random assignment (vs matching)

  4. Common Threats to Research • Confound • When an additional variable (nuisance variable) exists that may influence the dependent variable and that varies systematically along with the independent variable. • Confounds threaten internal validity. It can be reduced through random assignment and by holding conditions constant.

  5. Common Threats to Research • Artifact • Avariable that is held constant in a study but which influences the relation between the independent and dependent variables. • Artifacts threaten external validity. It can be reduced through random selection and maximizing experimental realism.

  6. Common Threats to Research • Noise- • Extraneous variable in an experiment that influences the dependent variable but that is evenly distributed across the experimental conditions. • Noise does not threaten validity, but it decreases the ability to detect an effect statistically. It can be reduced through the use of homogenous samples.

  7. Common Threats to Research • Person Confound • people who are high or low on this variable also happen to be high or low on some individual difference variable that is associated with the outcome variable of interest • Reduced or eliminated through random assignment

  8. Common Threats to Research • Procedural Confound • Researcher mistakenly allows a second variable to vary along with a manipulated variable • Eliminated by repeating the study while controlling for this variable

  9. Common Threats to Research • Operational Confound- when a measure designed to assess a specific construct inadvertently measures something else as well. It can be eliminated by refining the operational definition (measure).

  10. Strengths of True Experiments • Eliminate individual differences (person confounds) • Eliminate other kinds of confounds (procedural and operational confounds) • Pull researchers into the laboratory (controlled environment)

  11. Strengths of True Experiments • Allow researchers to observe the invisible (e.g. fMRI) • Provide information about interactions (through stats) • Minimize noise (reduced variability)

  12. Are True Experiments Realistic? • Problem: Artificiality • Solution: Two forms of realism (mundane and experimental)

  13. Two Forms of Realism • Mundane Realism- the degree to which the physical setting in an experiment is similar to the real-world setting in which the experimenter’s independent and dependent variables are most likely to operate

  14. Two Forms of Realism • Experimental Realism- the degree to which the subjective experiences of research participants are realistic or psychologically meaningful. Well-designed experiments can be high in experimental realism even when they bear little physical resemblance to the real world.

  15. Are True Experiments Realistic? • A recipe for experimental realism? • Manipulation checks throughout an experiment asking research participants about their experience • Deception

  16. Trade-Offs Between Internal and External Validity • There is a perceived conflict between internal and external validity because confounds threaten internal validity and artifacts threaten external validity.

  17. Trade-Offs Between Internal and External Validity • A highly controlled experimental design will eliminate confounds, but can also be considered an artifact. On the other hand, a loosely controlled experiment is often subject to many confounding variables. • Experiments that are high in either mundane realism or experimental realism tend to be high in both internal and external validity.

  18. Trade-Offs Between Internal and External Validity • Experimental versus nonexperimental strategies • Laboratory versus field experiments

  19. The “How-To’s” of Lab Studies • Setting the stage • Rehearsing and playing the part: • Be suave - Be honest • Be nice - Be a good liar • Be educated - Be attentive • Replicate as needed

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