2:1 allocation [General Sta­tis­tics]

posted by Helmut Homepage – Vienna, Austria, 2021-06-22 15:05 (34 d 09:07 ago) – Posting: # 22427
Views: 418

Hi Sundar,

welcome back to the forum!

» 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 [image]-script see there. It gives for an assumed CV 40% and T/R-ratio 0.95 targeted at 80% power:

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

If we desire a 2:1 allocation and want to preserve power, we need 13% more subjects than for the 1:1 allocation.

» Note: The 2:1 randomization is mainly due to transition arm.

What do you mean by that?

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