“…For each visit, we have the patient's medical record number (MRN), demographic information (e.g., age, gender, race, insurance), emergency severity index (ESI, a measure of the patient's severity and urgency), attending physician, time of arrival, waiting time to enter the ED (from the time of arrival until the patient enters the ED bed), and ED LOS (from the time when a patient enters an ED bed until a discharge order is written, following previous convention [Batt & Terwiesch, 2016Song, Tucker, Murrell, & Vinson, 2015]). In addition, each record has time-stamped medical and procedure orders, such as medication, laboratory, consult requests, and radiology orders, as well as the reason for a patient's visit (known as the primary complaint), and the disposition of the patient at the end of the visit (e.g., admission to hospital, discharge from ED, transfer to another health care facility).…”