Chapter 1 Research Methods External Validity

Chapter 1 Research Methods

External Validity

What is External Validity?  The degree to which the results of a study can be applied to other situations.

 Generalizability vs. Transferability

Threats to External Validity     

Subjects Pretest sensitization Expectancy Hawthorne effect Over generalization

Increasing External Validity  Careful definition of population and appropriate sampling from it.  Careful and complete description of all aspects of how the study was conducted

 Replication (complete or conceptual)

Major current concern regarding much health related research  Males vs. female subjects

Relationship between Internal and External Validity  Often inversely related (e.g., pretesting)  Must have internal to have external