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Keywords: data matching, non-inferiority margin, synthesis approach, two-confidence-interval approach, type I error rate, power
Non-inferiority (NI) assessment is often performed to evaluate whether a test treatment can preserve certain percentage of the treatment effect of an active control compared to the placebo control. Two approaches are usually applied for the NI assessment. One is the so-called synthesis approach and the other is the two-confidence-interval approach. To fully utilize available information, historical data of the active control may be borrowed not just for the NI margin specification but also for the actual NI assessment. In that case, the historical data will be used twice which may create some concern. Moreover, as the historical data have already been observed and fixed when the current NI trial is designed, the NI assessment with historical borrowing could be treated as a conditional analysis. In this research, we discuss the methods and the associated considerations including sample size calculation and type I error probability control for historical data borrowing for NI assessment. Simulation and an example are used to illustrate the applications and compare the characteristics of the methods.