HKSM

A technique to test alternative schedule scenarios by adjusting assumptions, constraints, or resources and observing impacts on dates, critical path, and utilization. It helps choose a feasible plan and prepare responses for likely disruptions.

Key Points

• Scenario-based evaluation performed on the schedule model, not on a static list of dates.
• Explores single-variable and multi-variable changes such as durations, logic, calendars, or resource limits.
• Highlights shifts in the critical path, total float, and resource bottlenecks.
• Can be manual (side-by-side scenarios) or tool-driven (what-if mode, simulation, or sandbox copies).
• Used iteratively during schedule development and when major risks or constraints change.
• Produces evidence for decisions on buffers, sequencing, and compression strategies.

Purpose of Analysis

• Assess schedule resilience to risks and uncertainties before committing to a baseline.
• Compare alternatives such as crashing, fast tracking, resequencing, or resource reallocation.
• Identify where to add reserves or management buffers for time-critical deliverables.
• Prepare contingency playbooks for realistic disruptions like vendor delays or outages.
• Support negotiation of deadlines and scope with stakeholders using objective impacts.

Method Steps

• Clarify the decision question and acceptance criteria (e.g., finish by a date with no added cost, or minimize overtime).
• Select variables to test such as activity duration ranges, leads/lags, resource availability, or calendar changes.
• Build scenarios in a copy of the schedule model, changing only the chosen variables.
• Run the model to recalculate early/late dates, float, and resource profiles with leveling rules as applicable.
• Capture results in a comparable format: key milestones, critical path list, slack, and resource peaks.
• Compare scenarios against criteria, document assumptions, and recommend the preferred option and contingencies.

Inputs Needed

• Schedule network diagram and activity attributes including predecessors, successors, leads, and lags.
• Estimated durations with ranges or uncertainty notes and productivity assumptions.
• Resource assignments, calendars, availability limits, and leveling rules.
• Constraints and deadlines from the schedule management plan and stakeholder commitments.
• Risk register items that could affect timing, especially high-probability or high-impact risks.
• Assumptions log relevant to work methods, vendor performance, or access windows.

Outputs Produced

• Scenario comparison summary highlighting impacts on finish dates, critical/near-critical paths, and float.
• Recommended course of action with trade-offs, such as added cost for crashing or risk exposure for fast tracking.
• Updates to schedule data like revised logic, adjusted calendars, and resource allocations.
• Inputs to risk responses and contingency plans, including trigger conditions and reserves.
• Stakeholder-ready visuals such as milestone deltas, path changes, and resource histograms.

Interpretation Tips

• Focus on path sensitivity: small changes that move a near-critical path to critical are early warning signs.
• Validate that resource constraints are enabled; unconstrained runs can hide real delays.
• Treat outputs as ranges, not certainties; prefer scenario bands over single-point promises.
• Check for calendar effects like holidays and maintenance windows when interpreting shifts.
• Confirm that changed assumptions are realistic and approved by the people who own the work.

Example

A deployment milestone is at risk due to possible two-week vendor lead-time variability. The team tests three options in a copy of the schedule.

• Base case: Keep current plan; finish date varies between June 10–June 24; critical path remains through procurement.
• Fast track: Overlap integration and testing by three days; finish improves by four days but increases defect risk.
• Crash: Add one senior engineer to integration; finish improves by seven days with an extra cost of $15,000.

The team recommends crashing with a defined budget and a testing contingency, as it meets the deadline with acceptable cost and risk.

Pitfalls

• Changing too many variables at once, making it unclear which factor drove the impact.
• Ignoring near-critical paths that can become critical under minor shifts.
• Running what-if without resource limits or calendars, producing unrealistic dates.
• Failing to document assumptions, making results hard to reproduce or defend.
• Choosing a scenario that meets the date but creates unsustainable overtime or quality risks.

PMP Example Question

A project’s key supplier may slip delivery by one week. The sponsor asks whether the milestone date can still be met without increasing cost. What should the project manager do first?

1. Direct the team to fast track the remaining activities to protect the date.
2. Perform what-if analysis on the schedule model to test scenarios with the potential delay.
3. Add a buffer to the milestone and update the schedule baseline.
4. Escalate to the change control board to request a deadline extension.

Correct Answer: B — Perform what-if analysis on the schedule model to test scenarios with the potential delay.

Explanation: Analyze impacts and alternatives before committing to actions or baseline changes. What-if analysis provides evidence to decide on fast tracking, buffers, or other responses.