# Confidence interval

From Citizendium, the Citizens' Compendium

The **Confidence interval** (CI) is a "range of values for a variable of interest, e.g., a rate, constructed so that this range has a specified probability of including the true value of the variable."^{[1]}

In large samples, calculations for the CI for rates and proportions may be based on the normal distribution.^{[2]}^{[3]}

The equation using the normal distribution is:^{[4]}

Where

For small samples, calculations should be made using the binomial distribution or the Poisson distribution.

## References

- ↑ Anonymous (2015), Confidence interval (English).
*Medical Subject Headings*. U.S. National Library of Medicine. - ↑ Fleiss, Joseph L. (1973).
*Statistical methods for rates and proportions*. New York: Wiley, 13. ISBN 0-471-26370-2. - ↑ Cochran, William Cox; Snedecor, George W. (1980).
*Statistical methods*. Ames: Iowa State University Press, 118. ISBN 0-8138-1560-6. - ↑ Gardner MJ, Altman DG (March 1986). "Confidence intervals rather than P values: estimation rather than hypothesis testing".
*Br Med J (Clin Res Ed)***292**(6522): 746–50. PMID 3082422.^{[e]}