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Simple randomization
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Best; random assignment prevents predictability
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Poor; likely to result in differences across cells
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Poor; likely to result in differences across cells
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Best; simple to implement
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Stratification with permuted blocks
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OK; Random order of assignments within blocks within strata reduces predictability but known block sizes increase predictability
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Very good; blocking improves balance, but this is mitigated by stratification
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Good; stratification improves equivalence on specific variables
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Very good; more complex, but solutions are widely available
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Maximum tolerated imbalance
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Very good; random assignment protects against selection bias until big stick is needed.
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Very good; results at or below maximum tolerated imbalance of samples
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Poor; No better than simple randomization
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OK; can be implemented in a range of available software, but requires coding
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Minimal sufficient balance
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Very good; random assignment protects against selection bias until biased coin is needed
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Poor; No better than simple randomization
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Very good; results at or below maximum tolerated inequivalence of covariates
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OK; can be implemented in a range of available software, but requires coding
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Minimization
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Poor when purely deterministic; improved with incorporation of random element
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Very good; should promote balance, depending on algorithm
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Best; promotes equivalence on a large number of variables
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OK; can be implemented in a range of available software, but requires coding
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