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 What are the two groups in experimental design?In a true experiment, the effect of an intervention is tested by comparing two groups. One group is exposed to the intervention (the experimental group, also known as the treatment group) and the other is not exposed to the intervention (the control group).
In which group design are participants randomly assigned to groups?In an experimental matched design, you use blocking and then match up individual participants from each block based on specific characteristics. Within each matched pair or group, you randomly assign each participant to one of the conditions in the experiment and compare their outcomes.
What two groups are needed for experimental conditions to take place?In order to determine the impact of an independent variable, it is important to have at least two different treatment conditions. This usually involves using a control group that receives no treatment against an experimental group that receives the treatment.
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