There is a basic difference between LiquidPlanner and most typical project management software packages -- the ability to add a range of time for the completion of a task. This seemingly small feature allows estimators to have a different solution to the conflict they experience now.
In the Theory of Constraints world, a "Evaporing Cloud" is used to represent this conflict. These clouds demonstrate the logic behind the conflict, to ensure there is understand of the conflict and the resulting action that is taken. Here's a simplified version:
It reads like this:
Using LiquidPlanner's range estimates also resolve the conflict. It challenges the C to D' link. We'll minimize waste by aggregating all of the task's variation to determine a 50% completion possibility (a 50-50 chance we'll finish on time) and a 98% Completion date. The difference between these two dates is the time buffer.
Is the time buffer wasteful? From a pure lean perspective, we would say that it is. But we can't eliminate all variation at one time, so we need buffers to absorb variation. We call this "profitable waste." Its waste because we should have variation, but its profitable if we are able to delivery our projects on-time greater than 95% of the time.
Thus LiquidPlanner's task range estimate is more than a feature -- its the method that resolves one of the major conflicts in Project Management. But the current conflict has a "chain reaction" impact that creates other problems (call Undesired Effects in the TOC world) that we'll talk about in our next post.