HKSM

Expert judgement is the use of qualified individuals' knowledge and experience to inform estimates and decisions. For estimating, experts provide effort, cost, or duration predictions based on analogous work, domain experience, and available data.

Key Points

• Relies on qualified individuals with relevant domain, technical, or business experience.
• Useful when data is limited, the work is novel, or speed is critical.
• Works best when structured (e.g., interviews, Delphi, workshops) and documented.
• Produces ranges and confidence levels rather than single-point estimates where possible.
• Combines expert opinion with historical data and lessons learned to reduce bias.
• Requires clear scope, assumptions, and constraints to keep estimates grounded.

When to Use

• Early in planning when detailed information is not yet available.
• For complex, innovative, or high-uncertainty work where analogies guide estimates.
• To validate or calibrate outputs from other estimating techniques.
• When historical data exists but needs interpretation for the current context.
• To quickly assess feasibility or set initial ranges for cost, effort, or duration.

How to Estimate

• Define the estimation scope: clarify deliverables, boundaries, and acceptance criteria.
• Select and brief experts: share the same inputs, objectives, and estimation scales.
• Choose a structure: individual interviews, a panel, or anonymous rounds (e.g., Delphi).
• Elicit estimates as ranges with assumptions, drivers, and confidence levels.
• Probe for rationale and reference data; ask for analogies and key risk factors.
• Aggregate estimates: use median or consensus, highlight spread and outliers.
• Document the basis of estimate, including assumptions, constraints, and data sources.
• Review and refine as new information emerges; update ranges and risks.

Inputs Needed

• Scope description, WBS or backlog items, and acceptance criteria.
• Historical data, benchmarks, and lessons learned.
• Constraints (budget, time, resources) and organizational policies.
• Assumptions log and risk register (initial risks, uncertainties).
• Resource calendars and team skill profiles.
• Definition of estimation units, range conventions, and confidence levels.

Outputs Produced

• Effort, cost, or duration estimates (preferably as ranges with confidence).
• Basis of estimates documenting assumptions, methods, and data used.
• Identified risks, dependencies, and open questions from expert insights.
• Updated assumptions log and risk register.
• Recommendations for further data collection or alternative estimating methods.

Assumptions

• Experts have relevant, current, and credible experience.
• Experts receive consistent and adequate information to estimate.
• Biases are mitigated through structure, anonymity, or facilitation.
• Contextual differences from past work are identified and adjusted for.
• Estimates will be revisited as better information becomes available.

Example

A project team must estimate the duration to onboard a new vendor. The project manager convenes a panel of procurement and operations experts. Using a brief and the last three onboardings as references, experts provide duration ranges and highlight key drivers like contract complexity and compliance reviews. The facilitator aggregates the results, documents the basis of estimate, and the team sets an initial range with 70% confidence.

Pitfalls

• Relying on a single expert, creating blind spots or overconfidence.
• Allowing anchoring or seniority to dominate group estimates.
• Failing to document assumptions and rationale, reducing traceability.
• Ignoring historical data or context differences from prior work.
• Producing precise single-point estimates that mask uncertainty.
• Skipping periodic re-estimation as new information emerges.

PMP Example Question

During early planning, detailed requirements are incomplete. The project manager needs initial duration estimates for major deliverables. What is the best next step?

1. Conduct a structured expert judgement session (e.g., Delphi) to produce range estimates and document the basis of estimate.
2. Wait until all requirements are finalized before estimating to avoid rework.
3. Assign a single senior engineer to provide a definitive single-point estimate.
4. Apply a fixed organizational productivity factor without consulting experts.

Correct Answer: A — Conduct a structured expert judgement session (e.g., Delphi) to produce range estimates and document the basis of estimate.

Explanation: With limited detail, structured expert judgement provides timely, defensible range estimates and captures assumptions. Waiting or using uncalibrated single-point figures increases risk.