Tests of hypotheses are the predominant methodology used in clinical research decision-making, but numerous published papers have established that tests of hypotheses can lead to suboptimal decisions and advocate the use of Value of Information (VOI) methods, which are based on Bayesian decision theory, instead. Accessible to both clinical researchers and healthcare professionals, this guide discusses VOI methods for interpreting current information on diagnostic tests and analyzing clinical trials, and is illustrated throughout with examples. It also includes solutions for determining optimal designs to provide additional information used in decision models.