Imbalanced Randomization in Non-Inferiority Trials
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Randomization is a common technique used in clinical trials to eliminate potential bias and confounders in a patient population. Equal allocation to treatment groups is the standard due to its high efficiency in many cases. However, in certain scenarios, the unequal allocation can improve efficiency. In superiority trials with more than two groups, the optimal randomization is not always a balanced randomization. Non-inferiority trials are clinical trials designed to establish a new treatment that is not much worse than the current treatment or control. In non-inferiority trials, additive margin with equal variance is the only instance with balanced randomization. A tool for sample size calculation for non-inferiority trials with additive or multiplicative margin with normal, binomial or Poisson distribution is available at http://www.statlab.wisc.edu/shiny/SSNI/.
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