HKSM

Forecast how long each activity will take based on scope, resources, methods, and constraints so a realistic schedule can be built and maintained.

Purpose & When to Use

• Determine how much time each defined activity needs to be completed under expected conditions.
• Used during planning after activities and resources are identified, and revisited whenever scope, resources, or risks change.
• Feeds the schedule model, critical path analysis, milestones, and time-related risk and cost decisions.
• Improves predictability by making assumptions, constraints, and uncertainty visible.

Mini Flow (How It’s Done)

• Review inputs: activity list and attributes, resource needs and assignments, calendars, scope details, assumptions, risks, and historical data.
• Engage estimators: involve the people who will do the work, relevant experts, and suppliers to validate approach and rates.
• Select techniques: use analogous (by comparison), parametric (rates × quantities), three‑point (optimistic, most likely, pessimistic), bottom‑up (roll up from detailed tasks), and reserve analysis as appropriate.
• Consider drivers: resource availability and skill, productivity, learning curve, work windows, dependencies, constraints, tools, quality standards, and known risks.
• Calculate durations: apply chosen methods, convert to working time using calendars, and where using three‑point, compute an expected value and a range.
• Assess uncertainty: add time contingency for known risks in activities or as task buffers; keep any management reserve separate from the baseline.
• Document the basis: sources, assumptions, methods, ranges, confidence level, and key constraints for each estimate.
• Update records: revise activity attributes, risk and assumptions logs, lessons learned, and schedule data; share for review and agreement.

Quality & Acceptance Checklist

• Each activity has a duration in working time units and aligns with the defined scope.
• Assumptions and constraints affecting time are clearly documented.
• Estimation method used and data sources are recorded and traceable.
• Resource calendars, availability, and skill levels are reflected in the numbers.
• Uncertainty is expressed as ranges and/or confidence levels; risk‑based contingency is visible, not hidden.
• Dependencies, leads, and lags are explicit and justifiable.
• Estimates are reviewed by the people doing the work and relevant experts.
• Units are consistent across all activities and milestones.
• The basis of estimates is stored for future updates and audits.
• Updates are triggered when scope, resources, or risk responses change.

Common Mistakes & Exam Traps

• Confusing effort (person‑hours) with duration (elapsed time), especially when resource availability is part‑time.
• Ignoring calendars and resource constraints, leading to calendar‑day estimates instead of working‑day estimates.
• Using analogous estimates when projects are not truly comparable, or parametric rates without validated productivity data.
• Providing single‑point numbers with no ranges or risk consideration, or hiding padding instead of using transparent contingency.
• Estimating without involving those who will perform the work, increasing optimism bias.
• Failing to update durations after approved scope changes or risk responses like crashing or fast tracking.
• Assuming adding people will always shorten duration, ignoring coordination overhead and task type.
• Misusing leads and lags to mask schedule problems rather than modeling real dependencies.

PMP Example Question

A specialist needed for a critical activity will be available only 50% next month. The team previously estimated the activity as 40 hours of effort over one week. What should the project manager do to improve the duration estimate?

1. Add a management reserve to the schedule to cover the risk.
2. Apply the resource calendar and re‑estimate duration based on 50% availability.
3. Add more people to the activity to keep the one‑week duration.
4. Ask the sponsor to confirm the one‑week deadline.

Correct Answer: B — Apply the resource calendar and re‑estimate duration based on 50% availability.

Explanation: Duration depends on resource availability. With half‑time availability, 40 hours of effort will span about two weeks of elapsed time, assuming no other constraints.