This comment or something like it should be at the top, because it's the main point about polygraphing. It's the process, not the answers that matter.

I knew a guy who did security clearance checking for the Three Letter Agencies for many years. He told be that if I ever had to do these interviews, I just need to pick good sounding lies and stick to them. He said it's the ones who try to be honest and introspective who get failed out.