IGEM:MIT/2006/Notebook/2008-2-15

Source: Margin_of_error

Calculating the margin of error for a survey
The standard error of a reported proportion or percentage p measures its accuracy, and is the estimated standard deviation of that percentage. It can be estimated from just p and the sample size, n, if n is small relative to the population size, using the following formula:

Standard error = $$\sqrt{\frac{p(1-p)}{n}}$$

95% confidence interval = 1.96*standard error