Estimating Techniques: Quantitative Methods and Expert Judgment

PMBOK v8 Definition

Estimating techniques involve various methods for forecasting variables needed to complete the project. Quantitative estimating techniques include numerical estimates of effort, duration, or cost. The six most common estimation techniques are: Expert judgment, Analogous estimating, Bottom-up estimating, Multipoint estimating, Parametric estimating, and Relative size estimation. Qualitative estimating techniques can be used together with quantitative methods.

Why It Matters for the Exam

This concept appears frequently in PMI exam questions testing your ability to select the correct estimation technique for a given scenario. Questions often present a project situation and ask which technique best applies, requiring you to distinguish between qualitative and quantitative approaches. Expect these questions in the Plan and Execute performance domains.

Key Points to Remember (for the exam)

• Six Core Techniques: Expert judgment, Analogous estimating, Bottom-up estimating, Multipoint estimating, Parametric estimating, Relative size estimation
• Quantitative vs. Qualitative: Quantitative = numerical estimates of effort, duration, or cost; Qualitative = estimates based on understanding processes, behaviors, and conditions
• Combination Allowed: Qualitative techniques can be used together with quantitative methods
• Expert Judgment Defined: Judgment provided based upon expertise in an application area, discipline, industry, etc., as appropriate for the activity being performed
• Multipoint Estimating: Uses average or weighted average of optimistic, pessimistic, and most likely estimates when uncertainty exists
• Key Inputs for Estimates: Scope of work, required resource types or skill levels, estimated resource quantities, and resource calendars
• PERT Included: Program evaluation and review technique (PERT) is listed among estimation techniques

Typical PMI Exam Example

A project manager is estimating the duration of a complex software development activity with high uncertainty. The team has historical data from three similar projects. The manager calculates duration using optimistic (10 days), pessimistic (25 days), and most likely (15 days) estimates. Which estimating technique is being applied?

Answer: Multipoint estimating (using PERT weighted average)

PMI Exam Traps

• Trap: Confusing analogous estimating with parametric estimating Reality: Analogous uses historical data from similar projects; Parametric uses statistical relationships between variables

• Trap: Believing qualitative techniques are less valid than quantitative Reality: Qualitative techniques can be used together with quantitative methods and are equally valid

• Trap: Thinking expert judgment is only for initial estimates Reality: Expert judgment applies throughout the project and across all estimation activities

• Trap: Confusing bottom-up estimating with multipoint estimating Reality: Bottom-up estimates individual activities and rolls up; Multipoint uses three-point estimates (optimistic, pessimistic, most likely)

Important PMI Connections

Quick Review Questions

1. A project team is estimating costs for a new construction project. They use data from three previous similar projects and adjust for size differences. Which estimating technique are they using?

2. When should a project manager use multipoint estimating instead of analogous estimating?

3. What is the key difference between qualitative and quantitative estimating techniques according to PMBOK v8?

4. A project manager has no historical data but has access to industry experts. Which estimation technique is most appropriate?

5. In which step of the planning process does estimating effort and duration occur, and what are its key inputs?

PMBOK v8 Reference

Section 2.2 - Scope Performance Domain Section 2.6 - Resources Performance Domain Section on Estimation Techniques (as provided in the RAG context)