Margin of Error

From the book, Chapter 10. Margin ≈ 1.96 × √(p × (1 − p) ÷ n) at 95%, roughly 1 ÷ √n for a share near half. A poll of 1,000 at 52% has a margin of about ±3.1 points; the margin on a 52–48 lead is about ±6.2. The margin covers only random sampling. It says nothing about who was missed, who didn’t answer, or how the question was worded.