First of all, I want to talk about Little’s law
The average number of work items in a stable system
is equal to their average completion rate, multiplied
by their average time in the system John Little, 1961
By solving this simple formula you are able to solve the
average time for work items in your system.
My closet provides a very good stable system example to
illustrate how you can apply Little’s law to track the average
Buying T-Shirts is one of my favourite hobbies, but I follow a rule,
I never buy a T-Shirt if I have the closet full (I only have space for 12).
Then I buy a new one and added to my closet. My closet is a stable system:
the rate at which T-Shirt enters the closet is the rate at which T-Shirt gets old.
Only 1 T-Shirt per month so per year, I buy 12 T-Shirt.
So, what is the average time for a book in my bookstore?
Let’s use Little’s law
Average number of work items in a stable system =
Average completion rate X Average time in the system
Using my closet terms
12 T-Shirt = 6 T-Shirt / year (to finish reading) X
Average time in the bookstore.
Thus, the average time a T-Shirt is in my closet is 2 years