Final answer:
Top-down estimating is unsuitable when a Work Breakdown Structure cannot be easily defined. It is still suitable for situations involving fixed-price contracts and when evaluating project proposals. Therefore, the correct answer is 'd) none of the above'.
Step-by-step explanation:
Top-down estimating for projects is least suited for situations when a) A Work Breakdown Structure (WBS) cannot easily be defined, as the estimate relies on the breakup of a project into smaller components. Option b) there are fixed-price contracts is incorrect because top-down estimates can be sufficiently accurate for use in fixed-price contract situations.
Finally, option c) project proposals are being evaluated is also not correct since top-down estimating is often used in the early stages of project planning, which would include proposal evaluation. Therefore, the correct answer is d) none of the above.
In the practice of estimation, having a clear idea about the relationships between variables is critical. To make progress, understanding how factors like time, cost, and resources interact will assist in developing more precise estimates.
Top-down estimating is an approach where the overall project cost is estimated from the top and then divided down to component levels for more detail. It is a useful method in situations where there is a historical basis for the estimate, the project is at an early stage, or when detailed information is lacking.