Monday, April 21, 2014

Personal WIP limit directly impacts Cycle Time

Personal WIP limit directly impacts Cycle Time. It is way better to tell your friend "I am completing 'this', when done I will help you out and before the end of the day we will resolve your problem" than "I am completing 'this' but I will IM you when I have some free time to start addressing your issue. The sooner we start looking into it the sooner we will resolve it after all".

Try limiting the amount of work you do at the same time and experiment the satisfaction of getting things done faster. Know your limitations and free yourself from stress.

Productivity should be measured and one of those metrics used in Lean thinking is called cycle time which is the time a unit of work takes from the moment we start working on it till the moment we are done with it.

If t1 is the time issue A will take to be resolved and t2 is the time for issue B to get resolved. Most likely the average cycle time for the resolver is (t1+t2)/2 however this is only considering issue A and B are queued. If on the contrary you try to address them at once your cycle time might be as worst as (2t1+2t2)/2 = t1+t2, literally duplicating your cycle time. You start issue A which takes t1 and issue B which takes t2 at the same time. You switch tasks taking slots of t1 for A and slots of t2 for B. If t1=t2 the worst case scenario is met. By the time you finalize them both (considering a perfect distribution of time slots and switching frequency) you will have burned 2*t1 to complete A and also 2*t1 to complete B. This means that any new similar item will take twice as much as it could take if you would be addressing it alone. Why sacrifice the delivery time of a unit of work which is completely independent from another?

Needless to say how bad this gets with WIP limits over 2. While a number 2 for WIP limits is OK I would challenge that the second item should be only pulled if we know the current bottleneck impeding us from moving with the first will be absolutely temporary. If the impediment will take too long we better negotiate the scope of the delivery or get help from the rest of the team to remove the impediment.

Respecting Personal WIP limits is of utmost importance.

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