Apr 30, 2012 03:59 PM|ziad18|LINK
ModifiedDate is just a DateTime field to store when a test or question or answer was created, or possibly updated.
Table Tests holds informations about all tests within the system (there are many tests and each on consists of multiple sections). If you have only one test you probably dont need table Tests.
I've got the full design as visio document, I dont know how to upload it in here