Which estimation approach is most accurate when there is detailed information about each task?

• A. Analogous
• B. Parametric
• C. Top-down
• D. Bottom-up

Answer: (D)

When you have detailed information about each task, you estimate the project by building up from the unit work to the whole. This bottom-up approach lets you assign specific durations, costs, and resources to every work package, then sum them to get the total. Because each task is analyzed on its own, the numbers capture the unique requirements, risks, and dependencies of that work, leading to a more precise overall estimate.

Other methods rely on higher-level data or comparisons. Analogous estimation uses similarities to past projects, which can introduce variance if those projects aren’t a close match. Parametric estimation depends on established relationships and data patterns, which may not perfectly fit every task detail. Top-down estimation starts with a project-wide figure and allocates it, potentially missing nuances at the task level. With rich task detail, bottom-up produces the most accurate results.