Compare and contrast topdown versus bottomup estimating and

Compare and contrast top-down versus bottom-up estimating and discuss how the project costs are influenced by the quality and accuracy of estimates.

Solution

Top-down estimates are typically used in the project conceptual phase, and depend on surrogate measures such as weight, square feet, ratios. Top-down methods do not consider individual activity issues and problems. Top-down estimates are good for rough estimates and can help select and prioritize projects.

Bottom-up time and cost estimates are usually tied directly to the WBS and a work package. These estimates are made by people familiar with the task, which helps to gain buy-in on the validity of the estimate. Use of several people should improve the accuracy of the estimate. Bottom-up estimates should be preferred if time to estimate is available, estimating cost is reasonable, and accuracy is important.