There's a goat behind door number 3: from Monty Hall to medicine.

In the 18th century, Thomas Bayes developed his eponymous theorem that teaches us that pretest probabilities can be altered by new information, such as when game show host Monty Hall revealed the goat behind one of the remaining doors in "Let's Make A Deal." Bayesian analysis is a key feature of many medical decisions. In this issue of the JCI, Lee and colleagues apply this concept to inflammatory bowel disease to identify gene expression-based biomarkers of disease severity. Importantly, these biomarkers allowed patients to be stratified into two groups: those at high risk for disease recurrence or the need for immunosuppressive treatment escalation and those with a more benign disease course.