Per this PFF article, Cam Newton ranked 8th most accurate QB, last week.
You'll note they compute their %s by adding dropped passes as if they were completed, thereby measuring just how many times a QB was on target.
Counting the 5 drops he suffered, as if they were completed (the assumption is that it's no fault of his they weren't), he comes up with 29 completions,of 37 pass attempts, for an adjusted "completion" % of 78.4.
So much for criticisms of his accuracy, huh?
The link above shows the Top 10 QBs, by adjusted completion %, and the Bottom 10, too.