Confidence Interval for Binomial Proportions

Newcombe (1998) suggests using alternatives to the usual Wald procedure to obtain confidence intervals for a proportion, particularly for proportions less than 0.2 or greater than 0.8. He suggests the exact binomial method and Wilson’s (1927) method provide slightly better coverage. Confidence intervals for both Wald and Wilson methods may be computed by using [attachment:BinomialCIs_wald_rev.xls this spreadsheet].

You can also obtain confidence intervals for the difference in two proportions [http://www.quantitativeskills.com/sisa/statistics/t-test.htm here.] Formulae used for the difference in proportions in 2x2 tables are described [:FAQ/ChiEqual: here].

• [:FAQ/BinomialConfidence/2gp:Confidence interval for differences in two independent binomial proportions]
• [:FAQ/BinomialConfidence/2gpp:Confidence interval for differences in two paired binomial proportions]

References

Newcombe RG. (1998) Two sided confidence intervals for the single proportion: Comparison of seven methods. Statistics in Medicine 1998;17:857-872

Wilson EB (1927) Probable inference, the law of succession, and statistical inference. J Am Stat Assoc 22, 209-212.

Last updated on 12 February, 2008