Experimental Designs Show
The Uniqueness of Experimental Methodology Experimental Control Determination of Causality Internal versus External Validity Another advantage of a well-designed experimental method is its high level of internal validity. A design that has high internal validity allows you to conclude that a particular variable is the direct cause of a particular outcome. In contrast external validity is often seen as a challenge for experimental work. External validity is the degree to which conclusions drawn from a particular set of results can be generalized to other samples and situations. The sample in a particular experiment may not represent the larger population of interest, and the experimental situation may not resemble the real-world context that it is designed to model because of its artificiality. The concern around artificiality is controversial and not shared by everyone who does psychological research. Key Constructs of Experimental Methods Independent and Dependent Variables Experimental
and Control Groups Placebo Effect Random Assignment Types of Experimental Designs Between-Subjects Designs Advantages of Between-Subjects Designs Disadvantages of
Between-Subjects Designs Within-Subjects Designs Advantages of Within-Subjects Designs Disadvantages of Within-Subjects Designs Matched Group Designs Advantages of Matched Group Designs Disadvantages of Matched Group Designs Confounding Factors and Extraneous Variables Participant Characteristics The Hawthorne Effect Demand Characteristics Other Confounds Strategies for Dealing with Confounds Hold Potential Confounding Variables Constant Vary Test Items and Tasks Use Blind and Double-Blind Designs Statistically Control for Variables that Can’t be
Experimentally Controlled Use Randomization and Counterbalancing Ceiling and Floor
Effects What Steele and Aronson Found Ethical Considerations in Experimental Design Placebo/Control Group and Denial of Treatment Confederates and Deceit How do you describe the levels of an independent variable?Levels of an Independent Variable
If an experiment were comparing five types of diets, then the independent variable (type of diet) would have 5 levels. In general, the number of levels of an independent variable is the number of experimental conditions.
Which of the following techniques include presenting levels of the independent variable to participants in different sequences?When researchers use counterbalancing, they present the levels of the independent variable to participants in different orders. With counterbalancing, any order effects should cancel each other out when all the data are collected.
Which kind of design expose participants to each level of the independent variable?In within-subjects experimental designs, each subject in the study is exposed to each level of the independent variable. Therefore, for each subject a score on the dependent variable is collected more than once (once for each level of the independent variable).
When each participant experiences all levels of the independent variable The independent variable is called a variable?A within-groups design is when each participant experiences all levels of the independent variable. There are two types of this design.
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