Certain embodiments involve data from places such as healthcare facilities to make predictions about actual expected procedure durations as well as other parameters such as the probability of a patient being late or being a no-show. Before scheduling a patient, the system will use these parameters to run a simulation that can then suggest time slots that maximize target service levels (for example, "patients should not wait longer than 15 minutes in 95% of the cases") and maximize facility efficiency (minimize the unutilized time between appointments).