Error Rates of Hand-Counted Voting Systems
The error rate for hand-counted ballots is about two percent.
All voting systems have nonzero error rates. This doesn’t surprise technologists, but does surprise the general public. There’s a myth out there that elections are perfectly accurate, down to the single vote. They’re not. If the vote is within a few percentage points, they’re likely a statistical tie. (The problem, of course, is that elections must produce a single winner.)