  It is generally believed that bias is minimized in well-controlled randomized
clinical trials. However, bias can arise in active controlled noninferiority
trials because the inference relies on a previously estimated effect size
obtained from a historical trial that may have been conducted for a different
population. By implementing a likelihood reweighting method through propensity
scoring, a study designed to estimate a treatment effect in one trial
population can be used to estimate the treatment effect size in a different
target population. We illustrate this method in active controlled
noninferiority trials, although it can also be used in other types of studies,
such as historically controlled trials, meta-analyses, and comparative
effectiveness analyses.
