Threats to Internal Validity (https://www.youtube.com/watch?v=_UPUtlHDM0A&list=PLo9NtuLffoEFebVxHHzB0i1ESULWp4dMW)

This online video, created by psychologist Natalie Boyd, provides an excellent, accessible introduction to the most basic threats to internal validity.

The Use of Field Experiments for Studies of Employment Discrimination

(http://scholar.harvard.edu/pager/publications/use-field-experiments-studies-employment-discrimination-contributions-critiques)

Box 8.1, which describes a field experiment on employment discrimination, makes reference to audit studies. In this article Devah Pager provides a thorough description and critique of the methodology of audit studies, including an appendix on how to design and implement a field experiment on employment discrimination.