As anyone who follows election polling can tell you, when you survey 1,000 people, the margin of error is plus or minus three percentage points. But the real-world margin of error of election polls is not three percentage points. Comparing those polls’ results with actual electoral results, we find the historical margin of error is plus or minus six to seven percentage points. 18 states 12 6 0 18 races 12 6 0 12 races 6 0 -10 pts -5 +0 +5 +10 President Senate Governor -10 pts. -5 +0 +5 +10 18 states 12 6 0 18 races 12 6 0 12 races 6 0 -10 pts -5 +0 +5 +10 President Senate Governor -10 pts.

Source: New York Times October 05, 2016 11:00 UTC