Dimensions of design space: a decisiontheoretic approach to optimal research design. Med Decis Making

Bayesian decision theory can be used not only to estab-lish the optimal sample size and its allocation in a single clinical study but also to identify an optimal portfolio of research combining different types of study design. Within a single study, the highest societal payoff to proposed research is achieved when its sample sizes and allocation between available treatment options are chosen to maximize the expected net benefit of sampling (ENBS). Where a number of different types of study informing different parameters in the decision problem could be conducted, the simultaneous estimation of ENBS across all dimensions of the design space is required to identify the optimal sample sizes and alloca-tions within such a research portfolio. This is illustrated through a simple example of a decision model of zanami