Indeed, that was second half of his question. It was the first half that I was answering. Your answer to the second half is correct.
If I use an 8mp camera and have high noise say at Iso 400 and I switch to a 5mp mode on the same camera still at Iso 400 will the pic be less noisy? What I am trying to detirmine is would it act as a 5mp camera with a large sensor. Hope this makes sense to someone.