Bottom-Up Estimating

Correct Answer: Combine the time estimates from all sub-teams, considering dependencies, to determine the project timeline.

The Best answer is to combine the time estimates from all sub-teams, considering dependencies, to determine the project timeline. This is the core principle of the bottom-up estimating method, which is used to develop an estimate by aggregating the estimates of the lower, more detailed levels of work. It's a more accurate method because it uses actual estimates from the people performing the work. Other choices are wrong because they either over-simplify the process such as choosing the longest time estimate provided by a sub-team and multiplying it by the number of sub-teams (it doesn't take into account that different teams may have different workloads), or involve methods that are not related to bottom-up method like using Critical Path Method (CPM) which is a step-by-step project management technique to identify critical tasks, or using analogues from past projects (analogous estimating), which doesn't ensure accuracy as no two projects are exactly the same.

Correct Answer: Bottom-Up Estimating

Bottom-Up Estimating is the most appropriate method for determining the overall estimate for the entire project when individual teams have already provided their estimates for their tasks. This is because Bottom-Up Estimating is a method of estimating project time and cost by aggregating detailed estimates of individual tasks or work activities. This means that the project manager would consider the estimates given by each team and then aggregate this data to form the overall estimate for the project. On the other hand, Top-Down Estimating is a method that starts with the total project and breaks it down into manageable components or tasks. This would not be suitable here as the individual team estimates have already been provided. Parametric Estimating uses statistical modeling to develop a cost estimate. It involves the use of project-specific data and statistical relationships to generate a cost estimate. It's often less accurate than the other methods as it doesn’t necessarily take into account the specific details of every task. Hence, it's not the best option for this situation. Finally, Analogous Estimating uses the experience of past projects to estimate the duration and cost of the current project. It is less time-consuming and costly than other techniques, but it may not be as accurate as Bottom-Up Estimating, especially if the past data used for estimation doesn't accurately reflect the current project's conditions.

Correct Answer: Aggregate the individual estimates from each contractor to calculate the total project budget, utilizing the bottom-up estimating technique.

The best approach for the project manager is to aggregate the individual cost estimates from each contractor to calculate the total project budget. This bottom-up estimating technique ensures that the budget reflects the most accurate and detailed information available from the contractors who are directly responsible for their respective work packages. The other options are less effective because they either ignore the detailed estimates provided by the contractors, attempt to fit the estimates into a predetermined budget, or assume that averaging the estimates will yield an accurate total budget without considering the specific scope and requirements of each subproject.