Unequal allocation randomization
Randomly assign study participants to unequally sized treatment groups
Unequal allocation randomization is a method of randomly assigning study participants to treatment groups in a disproportionate fashion. Unequal allocation randomization is used when the intervention, itself, is the focus of the experiment. Essentially, you want more people to receive the treatment so that treatment effects will be more precise and accurate. Ratios of allocation of 2:1, 3:1, and 4:1 to the treatment group are acceptable. The effect of unequal allocation "plateaus" at the 4:1 level.
When used with experimental research designs, unequal allocation randomization is used to study more serious disease states that require stronger treatments. The side effects of promising treatments can also be studied using unequal allocation.
From study participants' perspectives, unequal allocation may be more attractive for purposes of recruitment because they stand a much higher chance of being allocated to the treatment group. It is often hard to recruit enough participants to meet the stringent statistical power needs of experimental research designs.
There is an inherent loss of statistical power when allocating study participants in an unequal fashion. The empirical assumption of equipoise (equal groups at baseline) is often violated with unequal allocation randomization. Experimental research designs require more observations of the outcome
When used with experimental research designs, unequal allocation randomization is used to study more serious disease states that require stronger treatments. The side effects of promising treatments can also be studied using unequal allocation.
From study participants' perspectives, unequal allocation may be more attractive for purposes of recruitment because they stand a much higher chance of being allocated to the treatment group. It is often hard to recruit enough participants to meet the stringent statistical power needs of experimental research designs.
There is an inherent loss of statistical power when allocating study participants in an unequal fashion. The empirical assumption of equipoise (equal groups at baseline) is often violated with unequal allocation randomization. Experimental research designs require more observations of the outcome
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