Exact-corrected confidence interval for risk difference in noninferiority binomial trials

A novel confidence interval estimator is proposed for the risk difference in noninferiority binomial trials. The proposed confidence interval, which is dependent on the prespecified noninferiority margin, 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 and Zhang. 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.

Automated summary

A novel confidence interval estimator is proposed for the risk difference in noninferiority binomial trials. The proposed estimator is consistent with an exact unconditional test and has improved power, particularly for smaller sample sizes, compared to existing methods. The improved performance of the proposed estimator is theoretically justified and demonstrated through simulations and examples. An R package is also provided for implementing the proposed methods.