  A novel confidence interval estimator is proposed for the risk difference in
noninferiority binomial trials. The confidence interval is consistent with an
exact unconditional test that preserves the type-I error, and has improved
power, particularly for smaller sample sizes, compared to the confidence
interval by Chan & Zhang (1999). The improved performance of the proposed
confidence interval is theoretically justified and demonstrated with
simulations and examples. An R package is also distributed that implements the
proposed methods along with other confidence interval estimators.
