5.21 Perform Quantitative Risk Analysis
| 5.21 Perform Quantitative Risk Analysis | ||
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A data-driven assessment that models how identified risks and general uncertainty could change project cost and schedule, producing probabilities, ranges, and guidance for reserves and responses.
Purpose & When to Use
- Estimate the likelihood of meeting key dates and budgets using numbers, not just ratings.
- Size cost and schedule contingency based on modeled uncertainty.
- Identify which risks and assumptions drive the most variance.
- Compare alternatives or response strategies using expected value and scenarios.
- Use after qualitative risk prioritization, and on projects that are large, complex, or have tight targets or high uncertainty.
- Repeat at major milestones or after significant scope, estimate, or risk changes.
Mini Flow (How It’s Done)
- Confirm inputs and data quality: risk register with well-defined risks, schedule network, cost estimates, assumptions, and constraints.
- Build the model: add uncertainty to durations and costs (e.g., three-point estimates) and include discrete risk events with probabilities and impacts.
- Select distributions and dependencies: choose suitable probability distributions and model correlations where variables move together.
- Run analysis: use simulation for cost and/or schedule, perform sensitivity checks (e.g., tornado charts), and use decision trees or expected value where choices exist.
- Interpret results: review percentiles (e.g., P50, P80), ranges, probability of meeting targets, and the top risk drivers.
- Decide and update: propose contingency reserves, refine risk responses, adjust targets if needed, and update the risk report and risk register.
- Communicate and iterate: explain assumptions and confidence levels, then rerun when plans or risks change.
Quality & Acceptance Checklist
- Scope, schedule, and cost models reflect the current baseline and logic ties are valid.
- Key threats and opportunities are modeled, with clear probabilities and impacts.
- Uncertainty ranges for major estimates are justified and sourced.
- Chosen distributions and correlations are reasonable and documented.
- Outputs include percentiles, probability of meeting key targets, and a list of main risk drivers.
- Recommended contingency is traceable to analysis results, not arbitrary padding.
- Assumptions, data quality limits, and scenario choices are recorded.
- Stakeholders reviewed results and understand confidence levels and implications.
Common Mistakes & Exam Traps
- Confusing qualitative with quantitative analysis; quantitative uses numeric models and probabilities, not just risk ratings.
- Assuming it is required on every project; it is used when the benefit outweighs the effort and data is sufficient.
- Ignoring opportunities; include positive impacts as well as threats in the model.
- Leaving out correlations; dependencies between variables can materially change ranges.
- Using point estimates only; always include uncertainty ranges for key costs and durations.
- Misreading percentiles; P80 is not a guarantee, it is a confidence level under stated assumptions.
- Double counting reserves; contingency comes from analysis for known-unknowns, while management reserve is separate for unknown-unknowns.
- Running simulations on a weak schedule; missing logic ties or unrealistic calendars produce misleading results.
PMP Example Question
Your sponsor asks for the probability of finishing within the approved budget and a data-backed recommendation for cost contingency. You have already prioritized risks using likelihood and impact scores. What should you do next?
- Add a fixed percentage contingency based on organizational policy.
- Perform quantitative risk analysis using a cost model with uncertainties and discrete risks.
- Update the risk register with more qualitative categories.
- Request management reserve to cover unknown risks.
Correct Answer: B — Perform quantitative risk analysis using a cost model with uncertainties and discrete risks.
Explanation: The sponsor wants probabilities and defensible contingency. This requires quantitative analysis using a numerical model, not qualitative scoring or arbitrary percentages.
HKSM