How long does work sit in the system?
In a stable queue, average inventory equals throughput multiplied by average time in the system.
Inside this model
W=L/λ, where L is average items in the system and λ is completed items per hour. The chart shows time for a range of average inventories at the chosen throughput.
Out in the world
A practical use
Use tickets in progress and tickets completed per day to estimate average response time.
A useful lens. Not a universal law.
- The identity uses long-run averages in a stable system; a growing backlog cannot be summarized by one steady-state W.
Associated thinkers
Further reading
Explore the original research or the teaching reference behind this experiment.
John Little — A Proof for the Queuing Formula ↗