Bottom up estimating is a detailed cost or duration estimating technique that starts at the activity level. Which of the following statements about bottom up estimating is not true?

Introduction / Context:
Bottom up estimating is a technique where estimates are developed at the lowest level of the work breakdown structure and then aggregated to determine higher level estimates for work packages and the entire project. While this method can produce highly accurate estimates, it also requires detailed information and can be time consuming. The question asks which statement about bottom up estimating is not true.

Given Data / Assumptions:
- Bottom up estimating is applied at the detailed activity level. - The work breakdown structure supports this technique. - The options describe characteristics and limitations of bottom up estimating. - One statement must be identified as incorrect.

Concept / Approach:
Because bottom up estimating works at a detailed level, it generally requires a well defined and complete WBS. It tends to be more accurate when activities are clearly understood. However, it is resource intensive and may not be practical in the earliest planning stages when detail is lacking. Importantly, the effort required for bottom up estimating is directly related to the desired level of detail and accuracy. Therefore, it is not correct to say that the cost of using it is largely independent of accuracy or that it is always the methodology of choice.

Step-by-Step Solution:
Step 1: Evaluate each statement based on known characteristics of bottom up estimating. Step 2: Recognize that an accurate WBS is indeed needed, which supports option A as true. Step 3: Recall that smaller, well defined activities produce more accurate estimates, supporting option C as true. Step 4: Understand that bottom up estimating is difficult in early planning due to lack of detail, supporting option D as true. Step 5: Note that aggregated bottom up estimates can roll up to higher levels, supporting option E as true. Step 6: Identify option B as false because the cost of performing detailed bottom up estimates does depend on the desired level of detail and accuracy and it is not always the best methodology.

Verification / Alternative check:
To verify, consider a very large project with thousands of activities. Performing bottom up estimates for every activity at a very high level of precision would require significant time and resources. Project managers might instead use analogous or parametric techniques early on and reserve bottom up estimates for critical or high risk portions. This contradicts the idea that the cost of bottom up estimating is independent of accuracy and that it is always the preferred method.

Why Other Options Are Wrong:
Option A is true because bottom up estimating depends on a well structured and complete WBS. Option C is true because breaking work into smaller, clearly defined activities helps estimators provide more accurate figures. Option D is true because in very early planning, when details are not yet known, bottom up estimating is usually impractical. Option E is true because aggregated activity level estimates naturally roll up into work package and project level estimates.

Common Pitfalls:
A common mistake is to assume that more detailed estimating is always better, regardless of cost and schedule constraints. Another pitfall is to ignore the value of higher level techniques like analogous and parametric estimating in the early phases. Project managers should balance the need for accuracy with the effort required and apply bottom up estimating where it adds the most value.

Final Answer:
The statement that is not true is since the cost of using bottom up estimating is largely independent of the desired accuracy, it is always the methodology of choice.