We use statistical detection theory in a continuous-time environment to provide a new perspective on calibrating a concern about robustness or an aversion to ambiguity. A decision maker repeatedly confronts uncertainty about state transition dynamics and a prior distribution over unobserved states or parameters. Two continuous-time formulations are counterparts of two discrete-time recursive specifications of Hansen and Sargent (2007) . One formulation shares features of the smooth ambiguity model of Klibanoff et al. (2005) and (2009)  and . Here our statistical detection calculations guide how to adjust contributions to entropy coming from hidden states as we take a continuous-time limit.