Efficient Allocation of Patients to Treatment Cells in Clinical Trials With More Than Two Treatment Conditions

Objective:Clinical trials generally allocate patients to equal-sized treatment groups. The authors propose that it may be more efficient to allocate unequal proportions of the total sample size to treatments when more than two treatments are being compared. Method:This proposal is illustrated with two examples. One involved a comparison of three treatments and used a dichotomous categorical outcome. The other involved comparison of three treatments and used a continuous measure.Results:In both examples, a considerable increase in efficiency was realized by reducing the number of patients assigned to the placebo cell.Conclusions:Unequal allocation of patients to treatments should be considered when more than two groups are compared. Am J Psychiatry 1998; 155: 1446-1448