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Stat Med. 1998 Apr 30;17(8):873-90.

Interval estimation for the difference between independent proportions: comparison of eleven methods.

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University of Wales College of Medicine, Heath Park, Cardiff, U.K.

Erratum in

  • Stat Med 1999 May 30;18(10):1293.


Several existing unconditional methods for setting confidence intervals for the difference between binomial proportions are evaluated. Computationally simpler methods are prone to a variety of aberrations and poor coverage properties. The closely interrelated methods of Mee and Miettinen and Nurminen perform well but require a computer program. Two new approaches which also avoid aberrations are developed and evaluated. A tail area profile likelihood based method produces the best coverage properties, but is difficult to calculate for large denominators. A method combining Wilson score intervals for the two proportions to be compared also performs well, and is readily implemented irrespective of sample size.

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