ExactCIdiff: An R Package for Computing Exact Confidence Intervals for the Difference of Two Proportions

Authors

Guogen Shan, University of Nevada Las Vegas,
Weizhen Wang, Beijing University of Technology, Wright State University

Date of this Version

12-2013

Document Type

Article

Citation

The R Journal (December 2013) 5(2); Editor: Hadley Wickham

Comments

Copyright 2013, The R Foundation. Open access material. License: CC BY 3.0 Unported

Abstract

Comparing two proportions through the difference is a basic problem in statistics and has applications in many fields. More than twenty confidence intervals (Newcombe, 1998a,b) have been proposed. Most of them are approximate intervals with an asymptotic infimum coverage probability much less than the nominal level. In addition, large sample may be costly in practice. So exact optimal confidence intervals become critical for drawing valid statistical inference with accuracy and precision. Recently, Wang (2010, 2012) derived the exact smallest (optimal) one-sided 1 confidence intervals for the difference of two paired or independent proportions. His intervals, however, are computer-intensive by nature. In this article, we provide an R package ExactCIdiff to implement the intervals when the sample size is not large. This would be the first available package in R to calculate the exact confidence intervals for the difference of proportions. Exact two-sided 1 easily obtained by taking the intersection of the lower and upper one-sided 1 interval can be /2 intervals. Readers may jump to Examples 1 and 2 to obtain these intervals.