Margin of Error

The margin of error is the “plus-or-minus” half-width of a confidence interval — the most a typical estimate is expected to miss by, at a chosen confidence level. A poll of 53% “±3 points” means the 95% interval runs from 50% to 56%.

Two honest cautions are routinely ignored in headlines. First, the standard margin of error only accounts for random sampling error, not biased questions, non-response, or people lying — those can dwarf it. Second, when comparing two numbers (candidate A vs B), the margin of error on the difference is larger than on either one alone, so a “lead” inside the margin may be no lead at all.