How many years do i need to do in the military to get full benefits?

It depends on the outcome. If the person was discharged from service under other than dishonorable conditions, & served 90 days or more of active duty with atleast 1 day during a period of war time. They will receive the benefits because of disability. But if the said person is not disabled they must serve a minimum of 2 years     

The best sociological research method would have to be using experiments although it has some disadvantages as well