Click on the following links. Please note these will open in a new window.

1. Visit the following website and examine the chart to see an example of several spurious relationships.  http://utopiayouarestandinginit.com/2014/06/17/examples-of-spurious-relationships/
2. Read the article at http://sites.duke.edu/hillygus/files/2014/06/HillygusPB.pdf for an example of research involving additive relationships
3. Watch the following video for an explanation of random assignment to either a test group or control group: https://youtu.be/V_GIjFw6RZE