The range between the extremes of an optimistic and pessimistic prediction about future costs is called range of:

The "range of possible costs" describes the spread between the most optimistic (lowest cost) and most pessimistic (highest cost) estimates for a future activity. This range is a key output of cost risk analysis and techniques like three-point estimating. It quantifies the uncertainty inherent in the forecast, providing a more realistic financial picture than a single-point estimate. This approach acknowledges that future costs are not certain and can fall anywhere within this calculated range, allowing for better risk management and contingency planning.

B. Final costs: This term refers to the actual, historical costs incurred upon completion of the work, not a predictive range.

C. Scope costs: This is not a standard term in cost estimating; it is an ambiguous distractor. Costs are associated with scope, but this term doesn't define a predictive range.

D. Limit costs: This typically refers to a single-point constraint, such as a budget ceiling or a not-to-exceed (NTE) value, not a range of potential outcomes.

1. National Contract Management Association. (2019). Contract Management Body of Knowledge (CMBOK) (6th ed.). In Competency 2.3, "Cost and Price Analysis," the concept of range estimating is discussed as a method to quantify cost uncertainty by establishing optimistic and pessimistic boundaries. Section 2.3.3, "Cost Estimating Techniques," specifically covers methods that produce a range of possible outcomes rather than a single point.

2. Fleming, Q. W., & Koppelman, J. M. (2006). Earned Value Project Management (3rd ed.). Project Management Institute. Chapter 3, "Defining the Work," discusses the Work Breakdown Structure (WBS) and the importance of estimating work packages. Advanced estimating techniques, derived from PERT, use optimistic, pessimistic, and most likely estimates to define a range of possible durations and costs, reflecting the inherent uncertainty.

3. MIT OpenCourseWare. (2008). 16.852J / ESD.34J System Engineering, Lecture 11: Cost Estimation. Massachusetts Institute of Technology. The lecture notes discuss parametric cost estimation and cost uncertainty, explaining that estimates are often presented as a range (e.g., using optimistic and pessimistic values) to reflect the level of confidence and risk in the projection. (Available via MIT OCW).