Presentation on theme: "Experience Carefully Planned: Experimental Research Designs."— Presentation transcript:
Experience Carefully Planned: Experimental Research Designs
Laboratory experiments allow researchers to see how things turn out when one and only one thing is changed
Manipulation Random assignment (vs matching)
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.
Artifact A variable 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.
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.
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
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
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).
Eliminate individual differences (person confounds) Eliminate other kinds of confounds (procedural and operational confounds) Pull researchers into the laboratory (controlled environment)
Allow researchers to observe the invisible (e.g. fMRI) Provide information about interactions (through stats) Minimize noise (reduced variability)
Problem: Artificiality Solution: Two forms of realism (mundane and experimental)
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
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.
A recipe for experimental realism? Manipulation checks throughout an experiment asking research participants about their experience Deception
There is a perceived conflict between internal and external validity because confounds threaten internal validity and artifacts threaten 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.
Experimental versus nonexperimental strategies Laboratory versus field experiments
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