https://en.wikipedia.org/wiki/Randomized_controlled_trial#Randomization

University of Michigan - Ann Arbor

In a randomized controlled trial (RCT), ensuring true randomness requires implementing procedures that minimize both allocation bias and selection bias. Alongside ensuring randomness, researchers must design the trial to maximize statistical power. While assigning participants to equal-sized groups generally maximizes statistical power, unequal group sizes can sometimes provide more statistical power for specific types of analyses.

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