CAPM Practice: Explain when it is appropriate to use a predictive, plan-based approach

At project initiation, limited information is available, so estimates have wide ranges — typically ROM estimates with -25% to +75% accuracy (some sources cite -50% to +100%). As planning progresses and more information becomes available, estimates are refined to budget estimates, then definitive estimates. This reflects the cone of uncertainty in predictive projects.

**Why not A:** Bottom-up estimates require detailed work packages and activity-level information that is not available during project initiation. This level of detail comes during detailed planning, not at the initial concept stage when high-level estimates are needed.

**Why not B:** Parametric estimates using precise historical data require well-defined parameters and reliable cost databases. At initiation, project parameters are not sufficiently defined to support precise parametric calculations.

**Why not D:** A definitive estimate with plus or minus 5% accuracy requires detailed scope definition, complete work breakdown, and thorough analysis. This level of precision is impossible at initiation when the project is still at the concept stage with limited information.