How do we misinterpret? Common threats to validity Chapter 5 How do we misinterpret? Common threats to validity

People are Different Individual differences and “third variables” Selection bias and nonresponse bias

People Change History and maturation Regression toward the mean

The Process of Studying People Changes People The Hawthorne Effect Testing effects Experimental mortality (attrition) Participant reaction bias Experimenter bias

Moving from Three Threats to Two: Confounds & Artifacts Confounds: an additional variable varies systematically with the IV or with the DV Artifacts: important but overlooked variables that are held constant in an experiment Confounds threaten internal validity; artifacts threaten external validity

Key Terms from Chapter 5 Pseudo-experiment Control group Selection bias Nonresponse bias History Maturation Regression toward the mean Hawthorne effect Testing effects Experimental mortality Attrition Homogeneous attrition Heterogeneous attrition

Key Terms from Chapter 4 Participant reaction bias Participant expectancies Demand characteristics Participant reactance Evaluation apprehension Cover story Unobtrusive observations Experimenter bias Double-blind procedure Confound Artifact

Key Terms from Chapter 4 Double-blind procedure Confound