A preliminary report of an out-patient systems study in Sri Lanka.

Out-patient medical clinics in Sri Lanka often have long queues of patients waiting to see a doctor partly due to a shortage of doctors. To apply operational research techniques to optimize the functioning of the clinic, an initial step is to determine the distributional pattern of patient arrival times and the doctors' service times. The results showed that the arrival times of patients were time dependent. However, analysis of half-hourly data of inter-arrival times showed a negative exponential distribution. The doctor's service time varied from doctor to doctor and whether new or follow up patients were being seen. Each of the service times seemed to fit into an Erlangian distribution.