2:1 allocation [General Statistics]
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❝ Will there be any issue in adopting 2:1 (Test:Reference) randomization method in biosimilarity (BE) studies?
You will loose some power compared to equally sized treatment arms. For an -script see there. It gives for an assumed CV 40% and T/R-ratio 0.95 targeted at 80% power:
If we desire a 2:1 allocation and want to preserve power, we need 13% more subjects than for the 1:1 allocation.
n = 130 (1:1 allocation)
nT = nR = 65
power = 0.8035
n = 132 (naïve 2:1 allocation)
nT = 88, nR = 44
power = 0.7618
n = 147 (2:1 allocation)
nT = 98, nR = 49
power = 0.8060
❝ Note: The 2:1 randomization is mainly due to transition arm.
What do you mean by that?
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