I didn't have to complete an interview about job experience of skills, it solely focused on my background and getting clearance. After I applied, I was given a condition al job offer pending successful completion of the background investigation. I had to meet with an investigator to go over my history (employment, education, places I've lived, foreign contacts, drug use, criminals history). Unsurprisingly, it is very in depth and invasive. After this, they flew me out to complete a psychological evaluation and polygraph, which asked a lot of similar questions. If you fail the poly (a lot of people do), don't worry, they will bring you back again until you can pass it.