Dr. James Benneyan, Department of Healthcare Systems Engineering, Northeastern University College of Engineering
Boston, Massachusetts, USA
A flow principle proven in other industries is to schedule work (i.e., appointments) in increasing order based on the consistency or variability in their durations. That is, a type of job or appointment that typically takes a fairly consistent amount of time should be scheduled if possible before one that typically can vary more considerably in duration.
This Excel simulation demonstrates this principle and the benefit of ordering the day’s work from smallest-to-largest variation (that is, schedule more predictable appointments earlier in the day). To see this principle in action, open the file and go to the first tab ("Summary of Results"). The table and histograms summarize the waiting times for 25 days under each of the following two scheduling rules based on the variation in the lengths of each appointment type:
- Rule 1. Appointment types with smaller variation in duration lengths go first
- Rule 2. Appointment types with larger variation in duration lengths go first
The first rule schedules appointments in increasing order of their variation (i.e., standard deviation) from smallest to largest. The second rule schedules work in the opposite order, from largest to smallest. Each time you hit the "F9" key on your keyboard, you will see results for a new set of 25 simulated days. Note that the average wait is always smaller for the smallest-to-largest rule, sometimes dramatically so. This will improve flow and reduce delays at the current process step and, importantly, also at downstream steps.
Appointment type A (e.g., follow ups) may fairly consistently take 30 minutes plus or minus 5 minutes, whereas Appointment type B (e.g., new visits) may take 45 minutes plus or minus 15 minutes. Under Rule 1 (better) Appointment A is scheduled first, and under Rule 2 (worse) Appointment B is scheduled first.e