 margin of error. The term describes the biggest likely difference between results when polling, say, a random sample of 1,000 and if we talked with every American. Here's the general idea. Say a survey finds 52% favor candidate red and the error margin is plus or minus 3 percentage points. That means there's some chance as many as 55% back red, 52 plus 3. It could also be as few as 49, 52 minus 3.