Goldratt claims that the current method of generating task time estimates is the primary reason for increased expense of projects and their inability to finish on time. The commonly accepted principle is to add safety (aka: pad or slop) to generate a task time length that will essentially guarantee the step gets completed. He asserts that estimates for a task are based on individuals providing values that they feel will give them an 80-90% chance of completing the step, these estimates are further padded by managers above this person creating a length of time to complete a task that is excessive - as much as 200% of the actual time required. It is this excessive padding that has the opposite effect - guaranteeing the task will run full term or late. As counter intuitive as this seems, he provides examples of why this is the case. This predisposes the people on the project to consume the time estimate by:
Triggering the "student syndrome" in the resource assigned to the task - they have more than enough time to do the task, therefore they start the task late using up all the safety.
Encouraging multitasking. The safety is added knowing that the resource will not be able to focus on the task and hence encouraged to multitask on multiple projects at a time, which significantly impacts all projects.
Not claiming early completion. In order to preserve the safety concept in future projects, resources do not report tasks completed early. Obviously, though, there is no way to hide a late completion.
Theory of Constraints Primer
The book presents a primer for Theory of Constraints. This is done in the form of a lecture by a professor who has recently returned from a sabbatical at a large conglomerate that uses the Theory of Constraints. The discussion focuses on the current methods of measuring success at a work center (cost and throughput) and shows how they are contradictory to the success of the production line as a...