Statistics & Probability
Advanced

Margin of Error

Half-width of a confidence interval for the mean.

Formula

E=zσnE = z\frac{\sigma}{\sqrt{n}}

Variables

zCritical value
\sigmaStd dev
nSample size

Example

Larger samples shrink the margin

Did You Know?

The margin of error shrinks only with the square root of sample size, so quadrupling a poll halves its error.

inference