Actually it should flow in both directions. The PM estimates the cost of
the project bottom-up based on the projected costs of getting the required
work done. This is passed up to senior management for approval. Once
approved it flows back down to become the "top-down" budget. If it's NOT
approved, then the PM needs to advise senior managment that the only way
they can achieve their goals is to reduce the project's scope and be able to
give concrete reasons why the reduced budget is not adequate to achieve the
desired results. Otherwise what can you do in the scenario where the
top-down budget imposed by senior management only buys you 100 man-hours of
labour but once you prepare the plan you find that the minimum work required
to achieve the project's full scope is 500 man-hours? Of course, this
implies that the Project Manager himself is either a mid to senior level
manager himself or provides input to the decision makers so that he is
involved in the loop from the earliest stages of the process, perhaps
involved even before the decision is made whether the project should be done
at all.
--
Steve House [MVP]
MS Project Trainer & Consultant
Visit
http://www.mvps.org/project/faqs.htm for the FAQs