Margin of error - Wikipedia, the free encyclopedia
For a simple random sample from a large population, the maximum margin of error is a simple re-expression of the sample size n. The numerators of these equations are rounded to two decimal places.
Margin of error at 99% confidence \approx 1.29/\sqrt{n}\,
Margin of error at 95% confidence \approx 0.98/\sqrt{n}\,
Margin of error at 90% confidence \approx 0.82/\sqrt{n}\,
If an article about a poll does not report the margin of error, but does state that a simple random sample of a certain size was used, the margin of error can be calculated for a desired degree of confidence using one of the above formulae. Also, if the 95% margin of error is given, one can find the 99% margin of error by increasing the reported margin of error by about 30%.
