To understand the pros and cons of various designs and to be able to better judge specific designs, we identify specific threats to internal and external validity. Before we do so, it is important to ...To understand the pros and cons of various designs and to be able to better judge specific designs, we identify specific threats to internal and external validity. Before we do so, it is important to note that a (perhaps the) primary challenge to establishing internal validity in the social sciences is the fact that most of the phenomena we care about have multiple causes and are often a result of some complex set of interactions.
