A bootstrap-based test for establishing noninferiority in clinical trials.

A randomized, active-control clinical trial setting with the objective of testing noninferiority for a continuous response variable is considered. Noninferiority margin is based on the concept of preserving a certain fraction of the active control effect. Noninferiority is established if the ratio of the lower (upper) limit of the two-sided 95% confidence interval for the treatment difference to the estimated mean of the active control is greater (less) than a certain fraction. The nominal significance level is not maintained by the above confidence interval-based noninferiority test. We use bootstrapping to derive an accurate lower (upper) limit of the same confidence interval, which approximates the nominal significance level better and improves the power.